From The Bad Beginning, the first book, comes this quote: "He found himself reading the same sentence over and over. He found himself reading the same sentence over and over. He found himself reading the same sentence over and over."
In a later book, the author spends a page talking about deja vu, and following it, a copy of (almost) that exact same page talking about deja vu.
Yet another later book mixed normal text with mirrored text.
Yet another book states that "you should never, ever, ever, ever, ever, ever, ever, ever..." and then you turn the page and the entire next page is taken up by "...ever, ever, ever, ever, ever, ever, ever, ever, ever, ever, ever, ever, ever, ever, ever, ever..."
And yet another book features the trio falling down a very long elevator shaft. Two pages are pure black. Stop for a moment to consider how closely Handler/Snicket must have worked with his publisher to get the word counts to exactly fit the trick pages.
Another example mentioned how sometimes books would have passages that would seem to make no sense to people who were just skimming, to get them to go back and actually read the book. This was followed by a sentence about construction workers carrying a door.
Another book contained a long, boring, and appropriately circular passage about the Water Cycle, so that Lemony could slip in a secret message to his sister under the impression that anyone else would have stopped reading by this point.
No part of this book may be used, reproduced, destroyed, tampered with, or eaten without written permission except in the case of brief, possibly coded quotations embodied in critical articles, reviews, and subpoenas.
According to Wikipedia, when The Hobbit was published Tolkien wished for "Thrór's map to be tipped in (that is, glued in after the book has been bound) at first mention in the text, and with the moon-letters (Anglo-Saxon runes) on the reverse so they could be seen when held up to the light." This turned out to be prohibitively expensive and was left undone. The 'moon letter' version of the map has since been created in the 2004 deluxe edition.
In some editions of Daniel Handler's book Watch Your Mouth, the second half of the story is printed in burgundy.
Life of Pi ends with an extended conversation, written in script form, between the protagonist and two Japanese businessmen. The Japanese businessmen alternate between speaking to the protagonist in English and to each other in Japanese. The Japanese dialogue is denoted with a bold, paintbrush-like font.
The Neverending Story uses two different colors for the two reality levels in the book, or two different typefaces in cheaper printings.
The book is printed in three colors, although there are some variations between the different versions of the book. Normal text is printed in black, the word "house" appears in blue, and references to mythology are in red, with the addition of colored and Braille plates. "Minotaur" may or may not be struck out, depending on whether it's used during one of the aforementioned mythology references. In addition, there are a few instances of purple in the book as well, including the phrase "A Novel" on the front cover, the edition number, and one instance of a struck-out purple phrase in Chapter XXI. There are two different typefaces, which are used to represent the contributions of the elderly blind man, Zampano, and the twenty-something slacker, Johnny Truant, with a rare third typeface for "The Editors" — and even the accuracy of the typefaces is called into question. Mirror text is used on occasion; some pages have only a few words sparsely placed, and in odd orientations. A labyrinth is represented by a chapter consisting almost wholly of footnotes which refer to each other in a way that can only be described as labyrinthine. The vote is out on if it's good surrealism or pretentious crap.
Some paperback editions have covers that are smaller than the pages. The book is larger on the inside than on the outside.
Danielewski's second book, Only Revolutions, had two stories, one starting from the front and one from the back. With every passing page, a little less page space was given to the one story and a little more to the other story, until at the middle of the book it's exactly 50/50. (Oh, and there's a hint to the font colors in this novel.)
Danielewski's The Fifty Year Sword uses different colors of quotation marks to indicate different speakers.
"jPod" is a post modern novel by Douglas Coupland. Examples of this trope range from spending 16 pages listing prime numbers between 10,000 and 20,000, with one non-prime number added as a game, to random pop-up and spam emails repeated verbatim in the middle of a scene.
The children's book The Monster at the End of This Book has Sesame Street's Grover going to greater and greater lengths to keep the reader from turning the page (as he's afraid of the eponymous monster at the end of the book). He tapes pages together, attempts to nail them down, builds a brick wall, all to no avail. (It's okay, though, as the monster at the end of the book turns out to be himself.)
Another book, Oscar's Grouch Book, has Oscar the Grouch trying to get the reader to stop reading and leave him alone, through a series of similar tricks.
A mainstay of the Thursday Next novels. The most prominent example is the Footnoterphone, which enables Jurisfiction agents to communicate long-distance via the footnotes of the novels. Certain characters speak exclusively in "Olde English" or "Courier Bold," which are treated as foreign languages by the characters even though they are perfectly comprehensible to the readers.
In serious trouble at one point, she escapes into the Footnoterphone conduits. The story continues in the footnotes, while the main text is blank.
It's better than that: Thursday escapes into the footnotes, and her story then continues in parallel to the main text, in which the people she escaped from are trying to figure out where she has gone. This does, of course, leave the reader to decide whether to read the main text first, the footnotes first, or to switch between the two.
Thursday wows the Bookworlders by being able to tell who is speaking even when they turn off their dialogue tags (he said).
The most recent book includes a sequence in which Thurs is thrown outside the bounds of the BookWorld, resulting in several wordless pages in graphic novel format.
There is also a scene with characters fighting a mispeling vyrus which as the progretion of the vyrus grows teh speling geets progresivvly wers.
Not to mention the Bookworm's, which ex'crete apo's'trophe's & ampers&s.
Or the grammarvores who consume punctuation and grammar which have overrun Finnegans Wake.
Stephen King is known to have dabbled in this from time to time.
In Insomnia, certain characters' telepathic thoughts fade out and back in, signifying that something is wrong with them. The text of their thoughts actuallyfadesintoillegibility,thenbecomesclear and readable again.
In his later efforts (Lisey's Story, The Dark Tower volumes 4-7), King experiments frequently with changing fonts and typefaces.
His short story "Survivor Type" is written as the diary of a surgeon who is shipwrecked on a desert island. After he starts to go crazy and cut off parts of his own body for food, his entries become more erratic and nonsensical.
Another example used in almost all his works is when a sentence abruptly stops followed by some italicised words in the lines below in brackets before the sentence continues. This is usually done for characters who are currently stressed, and the line usually shows the characters' (subconcious) inner thoughts about what they are describing.
The very title of a short story by F. Paul Wilson was written by placing the words "DAVID", "COPPE", and "RFIEL" over each other, creating an unpronounceable jumble. The word itself was capable of sounding like the correct answer of any question or proposal to anyone hearing it (though not to the person saying it).
The novella Tiger! Tiger!, later expanded into the full-length novel The Stars My Destination, employs this excellently in the final two chapters. As the Anti-Hero protagonist Gully Foyle experiences synesthesia (a side effect of a nearby bomb blast), the text is written in an illustrative manner which reflects the confusion of his sensory apparatus.
In The Demolished Man, telepathic communication is represented by creative typesetting, sentences that can be read up, down, left or right simultaneously, rebuses, fonts and other trickery. Bester seemed very fond of this sort of thing in general.
An example: Two of the characters in this book are named @kins (Atkins) and 1/4maine (Quartermaine).
Babylon 5 is full of Shout Outs to Bester's work, down to naming a character Alfred Bester and giving him a Start of Darkness novel series with telepathic communication depicted as in The Demolished Man.
Another occurs in the short story Fondly Fahrenheit, about a schizophrenic mass murderer and his robot. At times the guy thinks of himself simply as himself, other times he thinks of himself as the robot, and then there's the times he thinks of them both as one person. All of this is accomplished by Bester constantly switching his use of pronouns.
In the Turing Hopper series by Donna Andrews, different typefaces are used for third-person narration vs. Turing's first-person commentary.
The 18th-century novel Tristram Shandy by Laurence Sterne includes such features as a black page when a character dies, and a blank one allowing the reader to sketch their vision of a female character's appearance.
James Dickey's poem "Apollo" from The Eye-Beaters, Blood, Victory, Madness, Buckhead, and Mercy, uses a black page to represent the communications blackout that occurred when Apollo 8 first orbited the moon.
Older Than Print: An elegant example of this can be found in The Tale of Genji, the seminal novel of Heian-era Japan, in which the 42nd chapter, "Vanished into Clouds", is left blank entirely after the title — the subtle implication being the death of the title character.
Peter David's novel I, Q, working from the point-of-view of Q during the apocalyptic end of the universe, uses a few of these tricks. Data raises his voice above all other noise by rapidly increasing his font size. And near the very end, Q, spitting in the face of death, writes the book up and stuffs it into a bottle which he then hurls into the whirlpool sucking up all existence. The last sentence is cut off halfway (as Q is screaming his defiance of fate), and then followed by not a few completely blank pages. And when you're finally wondering what the heck is up, you run across a few pages of laughter. Seems God was so amused by Q's defiance that she (God) decided to cancel The End.
Vendetta (also by Peter David), did this when a character reached Warp 10. She got stuck in a time loop, so naturally her one-page chapter began to repeat every few chapters, then every other chapter, then for several chapters in a row, until finally it stopped in mid-sentence ("just a few more seconds...") and the next chapter had the Next Generation crew musing about what her existence might be like now.
The Raw Shark Texts by Steven Hall features a scene where a conceptual shark (don't ask) is swimming toward the narrator, and the reader is treated to 45 pages of an ASCII shark getting slowly bigger and bigger as you flip the pages.
At one point, Interworld has the bottom quarter of a page go completely black, to symbolize the main character losing his memories.
The text for "The Mouse's Tale" winds down the page and narrows to a point, resembling a mouse's tail.
In the beginning of the sequel, an illustration of Alice going Through the Looking-Glass is matched up on the other side of the leaf with an illustration of her arrival. The second of these illustrations — the one showing Alice's arrival in Looking-Glass House — has Sir John Tenniel's distinctive monogram mirror-reversed.
Similarly, Karen Hesse's novel The Music of Dolphins is told by a young girl who was Raised by Wolves (or dolphins, as the case may be). At the beginning, the text is quite large and written in very simple sentences; as the narrator learns more English, the font size decreases and the breadth of vocabulary increases. She eventually has a breakdown and goes back to the ocean, forcing the text to return to its original simplified state.
The Athenian Murders by José Carlos Somoza played with this similarly to House of Leaves, with an apparent ancient Greek mystery being the bulk of the book and various footnotes telling other stories. One set of footnotes is by the original translator who was rumoured to have been murdered in the same fashion as the characters in the text, and another set of rare footnotes apparently by the editors of the copy you are actually reading. Most of the footnotes are from the current translator who is driving himself crazy, convinced that there is a hidden message in the translated text, and becomes convinced that the characters in the text are interacting with him. Eventually, it's revealed that both translators are fictional characters, and the entire book and all its footnotes was written by someone else. (Who, to make matters more confusing, wrote himself as one of the minor characters in the Greek mystery, making the translators characters created by someone in the text that they are translating.)
When Henry Esmond one of the novels of Victorian author William Makepeace Thackeray came out, there was a special edition made to look like an eighteenth century novel in binding and font (it is a pastiche of such works).
In the Boris Akunin novel Leviathan, text in chapters written from the perspective of a Japanese is rotated ninety degrees. It doesn't really look like Japanese vertical writing, but it does look "exotic".
In The Eye of the World which begins the Wheel of Time series, an arc spanning several chapters is told in a disjointed series of flashbacks. Near the end, Rand, the focus of the arc, "wonder(s) if his whole sense of time was getting skewed". Fans speculated endlessly on whether this was deliberate editorial commentary or just an accident.
The Interior Life by Katherine Blake postulates an unexplained mental connection between an ordinary woman in our world and a mage in a fantasy universe; each one ends up advising the other on her problems. A fairly subtle font change is used to distinguish between the two points of view. (Out of print, but highly recommended if you can find it in a used bookstore.)
In Gridlinked by Neal Asher, the main character has a computer-"augmented" brain, which allows him to wirelessly communicate with other people, AIs, and computers. These communications are written in a different font from the rest of the book.
In The General series by David Drake, S.M. Stirling and Eric Flint, some of the characters mentally communicate with an artificially intelligent computer (The other "ghost" that appears later in the series is just a simulation run by that computer.) The strangeness of its manner of speaking is described in detail, and its statements are written in bold and without capital letters. Even more interesting, sometimes The Center _uses_ capitals. And characters comment on that.
Nineteen Eighty-Four consistently describes a certain radical book being said by characters either in italics or in a completely different font. It's even pointed out in the narrative text.
As usual, William Gibson goes for broke; his poem "Agrippa — A Book of the Dead" (about his dead father) was first released on an encrypted, uncopyable diskette that deleted itself as you read. The book version was printed in photosensitive ink, disappearing after prolonged exposure to light.
In the aftermath of the rape in Self, the text is split into two columns per page, presumably to be read at the same time. Sometimes one or both of the columns feature large amounts of blank space.
J. K. Rowling used it occasionally in the Harry Potter series, often with letters that'd be in a font made to resemble handwriting. Different people had different handwriting. In one instance, there's two blurry blobs on the page, and Hagrid explains in the letter that he smeared some of the ink with his tears. Funetik Aksent was also used.
In Jonathan Safran Foer's Extremely Loud & Incredibly Close a father, writing to his dead son, mentions how he wishes he had an infinitely long book with which to write in, because he fears that at his current rate his words will start to slam into each other and become illegible. Farther along the letter the words do begin to get closer, then words start being printed on top of other words, and then the page is completely black.
The young protagonist Oskar solicits advice from a randomly-chosen clerk at an art store, seeking guidance in his search for information about his father, who died in the Twin Towers; later, the reader learns the entire episode is something of a red herring. The clerk mentions that when patrons scribble with a pen (in the store) to test it, often they write the name of a color, but rarely do they write in a different color than whichever word they're writing which names a color (such an act, she contends, would be psychologically unsettling). For example if you're testing a red pen you'd write "red" (all of this might help Oskar determine whether a slip of paper he'd earlier found—on which "Black" is written—refers to someone named So-and-so Black, or merely the color). The passage is accompanied by an "extra" page in the book, in which names of colors are written in different handwriting, at various angles (as if it were an oft-used scrap of paper from the store).
In Summon the Keeper by Tanya Huff, when one of the mundane characters hears the voice of Hell for the first time and tries to explain it to the protagonist, she asks if it sounded like it was speaking in all capitals, which the author did.
In Animorphs, the characters have the ability to communicate via telepathy or 'thought-speak' while in an animal form (as well, the alien Ax uses it when in his normal, mouthless body as his standard form of communication), and dialogue in thought-speak is indicated by the use of the '<' and '>' symbols instead of quotation marks.
In Dan Abnett's Gaunt's Ghosts novel Only In Death, the interchapter documents are printed in different fonts, and not straight on the page.
In C. S. Lewis's Till We Have Faces, the last portion of the book is written in italics, to show it's not the same handwriting as the rest of the book. (The narrator had died in the middle of writing a sentence; a final note was written by one of the people who found the body.)
In the Whateley Universe, the superheroes Team Kimba have their own deviser-built communications system. When they're sub-vocalizing and talking over it, the dialogue is in <> instead of quotes, and marked with the codename of the speaker when the voice would be recognizable.
Walter Moers does these quite often. To name a few examples:
In The 13 ˝ Lives of Captain Bluebear, the font changes when the eponymous character is having an encyclopaedia moment and grows when a giant spider is running after him.
In the City of the Dreaming books, the main character is flipping through a book, and finds what he's looking for at the end of the right page. Both the character and the reader turn page, and BAM!
You have just been poisoned. You have just been poisoned. You have just been poisoned. You have just been poisoned. You have just been poisoned. You have just been poisoned. You have just been poisoned. You have just been poisoned. You have just been poisoned. You have just been poisoned. You have just been poisoned. You have just been poisoned. You have just been poisoned. You have just been poisoned. You have just been poisoned. You have just been poisoned. Repeated for the full double page. The pages following this little surprise are black and the text is in white font, as the main character faints due to the poison.
A similar thing happens in Ensel and Grete. Whenever the Author of the book disrupts the flow of the story to digress and talk about what he feels like, the font changes. At some place several pages of the word Brummli are written to terrorize the reader.
Bram Stoker's Dracula is a series of letters between many of the characters. The reader is intended to interpret the novel as a bound collection of letters, and each includes headers with dates and signatures. It's very effective at drawing some readers in, especially since the viewpoints sufficiently show different characters' personalities, but it can also seem disjointed, since it switches around a lot and (usually) looks like normal fonts pretending to be letters.
In What My Mother Doesn't Know by Sonja Sonnes, a 15-year-old girl tells her story in verse, though it progresses like a normal novel. The poetry experiments with several textual plays like e.e. cumming's style.
Don Marquis' archy and mehitabel, and other books in the series, are written from the perspective of Archy the cockroach, entirely in lowercase letters... because Archy can operate an old-fashioned typewriter by painstakingly hopping on the keys, but he can't hit shift at the same time! (Marquis would later handwave reader queries about how Archy handled the carriage return.) The shift key got locked down for (part of) one poem, titled "CAPITALS AT LAST."
In Still Life With Woodpecker the author alternates between writing a story and writing about himself writing the story. In the final chapter his typewriter breaks down and he is forced to finish in longhand.
Elizabeth Bear's Blood and Iron has a relatively subtle one. For the majority of the book, every character uses third person narration. After one character sells her soul her narration switches to first person — the implication being that she was telling the story all along, but is no longer the same person.
Iain (M.) Banksloves these. In Complicity, for example, one narrator's chapters are written in first person, while the other's are told in second person. Most infamously, Feersum Endjinn has about a third of the text written in Funetik Aksent. One of the characters (Bascule) is keeping a journal, but some kind of brain dysfunction makes him spell phonetically. It was woolseyized as containing absolutely egregious amounts of orthographic and spelling errors in the Polish version.
In Dune, some words like "SPICE" and "VOICE" tend to be printed in capital block letters to give them a sort of mystical echo (see above for DEATH in the Discworld novels). However, there are no capital letters in the Hebrew language, so the Hebrew translation has these words printed in bold and in a larger typeface than the rest of the sentence. This method makes them even more creepy and resonant than the original, if at all possible.
Most editions of The Bible in English print the word "LORD" in all-capitals and sometimes in blockier font. Also, to a lesser extent, the use of a capital letter in the words "He, "Him", "His", when referring to the monodeity.
This extends past the Bible. In most (if not all) denominations of Christianity, it's considered appropriate to always capitalize pronouns when referring to God.
A different version of this can be found in the Hebrew Bible, where God is often referred to by the Tetragrammaton (the "explicit name" often transliterated in English as "Yahweh" or "Jehovah"), which (unlike the rest of the text) completely lacks diacritics, causing it to stand out rather starkly against the rest of the text. Some instances of the all-capital "LORD" mentioned in the previous point are intended to convey such contexts.
The Hebrew diacritics are not that old. An older practice (not sure how widespread) was to write God's name in Phoenician script, with the rest of the text in Aramaic letters.
Martin Luther's translation of the Bible to German uses "Herr" ("lord" in his era, more like "mister" today) when referring to humans, "HErr" when God is referred to as "Adonai" (or Jesus as "Kyrios") in the original text, and "HERR" when it's "JHWH". Modern editions often still use "Herr" set in small caps for the last variant.
Note: German capitalizes all nouns, not just proper nouns as in English. Hence the special capitalization to distinguish nouns referring to the Deity.
It has also become somewhat popular among Christians (particularly in America) in the last century to print Jesus' speech in red. The color itself represents His blood sacrifice and the practice has the functional purpose of distinguishing his speech from the other text as it doesn't include quotation marks.
'Red Letter Christians' take their name from this, as they only follow the red letters.
The Alcatraz series by Brandon Sanderson uses text formatting to make jokes on several occasions, including printing part of it uʍopəpısdn.
The young adult comic fantasy Rogues To Riches includes a scene where two thieves talk their way out of jail by convincing their guard that he's just a mook in a story, and will probably die if he tries to stop them, as they're the heroes. However, if he foolishly lets them go, he'll be promoted to comic relief instead, and might just rate an appearance at the end of the book. Sure enough, the very last page shows the stupid guard sitting in the thieves' former prison cell, wondering if he'll appear at the end.
A Wayside School book had a chapter where a character is forced to write a story backwards (end is at the beginning and vice versa). As you might have guessed, the chapter itself is written backwards.
Also, whenever a character in the Wayside School books is upside-down for some reason (i.e., hanging from the monkey bars) their dialogue is printed uʍop-əpısdn.
And chapter nineteen is always weird or missing, like the nineteenth floor of the school.
The Bartimaeus Trilogy has the eponymous character's self-narrated chapters anecdoted with footnotes that digress from the current situation in some manner. Later, the reason given that these only appear in his chapters is due to him having a multi-tracked mind, in that he can hold several lines of thought simultaneously. As he says, the best he can do to simulate the effect for us is footnotes.
This is teased deliciously in the third book of the trilogy, Ptolemy's Gate. Bartimaeus and Nathaniel are sharing a body and reading each others' minds toward the end. At one point (in one of Nathaniel's chapters, no less!), Bartimaeus starts a footnote describing one of his old buddies. The footnote is interrupted, and when you jump back to the text that it sprung from, Nathaniel is thinking at Bartimaeus to stop thinking in two directions because it makes his head hurt.
In A Prayer for Owen Meany, the text is all in caps IN AN ATTEMPT TO PROPERLY CONVEY THE EPONYMOUS CHARACTER'S DISTINCTIVE VOICE.
Marjorie B. Kellogg's Dragon Quartet books use different fonts for each of the four dragons (at least in the first three books).
D.J. MacHale's Pendragon series uses different fonts to indicate whether the reader is reading the journals Bobby is sending to his friend Mark, or whether he's reading the narrative of Mark's life on Second Earth.
Georges Perec's "La Disparition" (English title: A Void) entirely consists of words without the letter "E" in it.
One series, the Fire Within, had a scene that went something along the lines of: "'I can't believe how much I don't understand about this silly family and their crazy dragons,' David said. Liz put a hand to her forehead and spoke, 'David, please stop talking in italics.'"
In the hardcover of The Princess Bride, "Goldman"'s interjections on the text are printed in red ink, while "Morgenstern"'s text is in black. In paperbacks, Goldman's parts are usually in italics.
Dan Simmons's novel The Terror features chapters written from various characters' points of view. One of them, a surgeon, has his written as diary entries. The one time he gets a normal chapter, it's mentioned that he was too tired to write. He later poisons himself and mentions that his mind will start to deteriorate. His spelling becomes worse and worse, random capitals are inserted everywhere, and letters and words are skipped entirely.
In Joan Hess's Claire Malloy mysteries, Claire's daughter speaks in Capital Letters when she's being overdramatic. Lampshaded in the narrative by Claire herself.
Chuck Palahniuk's Survivor numbers chapters backwards as a countdown to the crash of the plane in which the narrator is squatting, telling the black box the story of his life, expecting a miracle, or not.
Tom Clancy's novel Patriot Games uses this twice. The narrative is going on, describing a nice British park when suddenly the text cuts off. The word BOOM! is printed in bold in the center of a large blank space. This signifies the sudden and dramatic impact of the grenade that the ULA uses to disable the Prince of Wales's car. Later in the book, the chapter title is used to dramatic effect. The end of a chapter has Robby Jackson crouched on Jack's bed with a loaded shotgun, looking through a small window between rooms at where his wife, his close friends, and the Prince and Princess are being held hostage. The chapter ends with something like "Finally, he moved close to the other one." The next chapter begins by describing how fast pellets from a shotgun disperse. The title of the chapter (printed in huge bold font?) is "THE SOUND OF FREEDOM".
In Harlan Ellison®'s short story I Have No Mouth and I Must Scream, the supercomputer AM describes its hate for humanity to Ted, the narrator, in a burning neon pillar of stainlness steel rammed into his soft grey brain matter. Yeah... it's kinda like that. Anyway, the computer's words are written in block capitals in a single thin column in the centre of the page.
Ellison also uses depictions of strips of punchcode tape,note encoded in International Telegraph Alphabet No 2 similar to that used in teletypewriters. There are two alternating messages: "I THINK, THEREFORE I AM" and "COGITO ERGO SUM." The author claims that from the story's first appearance in 1967 until its publication in 1991 in The Essential Ellison, every printing corrupted what he called AM's "talkfields."
Pretty Maggie Moneyeyes, from the same short story collection, uses this trope to a greater extent to give a disorienting impression of the moment of death, by using short, unrelated abstract phrases separated by circles, as well as smaller text in a continuous block to show Maggie's soul being trapped in the slot machine she was playing. Again, it's kinda like that. In the introduction Ellison acknowledges the limitations of his medium and calls all this "experimentation" into expanding it. In interviews he has also claimed that the overall look of a page of writing in a book is relevant to the impression he wants it to create; one reason why he hates computers and writes all his stories on a typewriter.
In L. Jagi Lamplighter's Prospero In Hell, the demon possessing Theo speaks in italics and ALL CAPS.
The Provost's Dog books are presented mostly as the journals of Beka Cooper, the protagonist. There is the occasional mispelling, especially when she is sick or exhausted. At one point, she falls asleep while writing and one of her words trails off into a wavy line running down the page. There is also a page where her cat jumps onto her journal, leaving a blob of ink where the inkwell is spilled, and a set of inky pawprints on the page.
In the Real Life "Baconian Cipher" (not actually a cipher, rather, a steganographic code), developed by Francis Bacon, two different typefaces (bold, italic, a different font, adifferentfontcolour, etc.) stand for the bits of a binary encoding, so that every five letters represent a single letter of a hidden text. It has, therefore, been suggested by some that Bacon in fact might have hidden clues to the supposed "fact" that he wrote William Shakespeare's plays by using this ciphe-er, steganographic code.
In The Years of Rice and Salt by Kim Stanley Robinson, the format of the book changes to match the historical era each section is set in. At the beginning, chapters have elaborate descriptions and the prose is frequently interrupted by poetry. Gradually, the prose becomes more solid, the chapter headings shorten to just titles, then numbers, and then nothing but a blank spot between them and the next chapter.
In a very subtle example, in The Paths of the Dead, the word "brandy" is always written in italics, as is usually done for words in foreign languages. This is because the book is ostensibly an in-universe novel written by a Lemony Narrator Dragaeran, whose native dialect lumps brandy together with other fruit-derived alcoholic drinks as "wine".
In the book of Fear and Loathing in Las Vegas, the "editor" makes a note that, for some time from that point on, Duke's writing is so chaotic—and so stained with various materials—that it's practically impossible to make out what exactly he was writing about. The editors explain, to the best of their ability, what they were able to piece together of the story from the mess, then they print a transcript of a section of audio tape of Duke and Doctor Gonzo talking to a woman. The movie achieves a similar function by having Duke—with no memory of the previous night (or nights)—try to make sense of his jumbled, damaged tapes, the film playing a montage of disconnected scenes for what's on the tape.
In Horatio Hornblower, it's well-established (if one reads in order of publication) that William Bush isn't very imaginative. Come Lieutenant, which is told from his point of view, there is a noticeable lack of the vivid metaphors and similes that pepper Hornblower's narration. One chapter sneaks some in by describing how interesting and beautiful a pulley rig on a cliff would look to someone other than Bush, who just sees a couple of ropes.
Hard-Boiled Wonderland and the End of the World does this. A lot of books will have the title written on the top of the book's pages. During Hard-Boiled Wonderland and The End of the World, the "Hard-Boiled Wonderland" chapters simply have "Hard-Boiled Wonderland" written at the left, whereas "The End of the World" chapters have "The End of the World" written on the top right.
In the Relativity series, flashbacks are in blue text. (Provided you're reading them online, or on an e-reader with a color screen. At any rate, they are set off from the main text by "<<<" and ">>>" so even in a black-and-white format, you can clearly see where the flashbacks are.)
In the book The Name of this Book Is Secret by Pseudonymous Bosch, the entire first chapter has been replaced by strings of Xs (because it's a secret).
In the Polish young reader book Cyryl, gdzie jesteś? (Cyryl, Where Are You?), two of the numerous viewpoint characters (the ones who aren't in the city where the majority of the plot takes place) have their own font style (italic and all-capitals text) used to describe the events in which they participate. Also, every few chapters, there are fourth wall-breaking musings from the author; these are depicted as hand-written notebook pages, even with some words striked out and replaced by others.
Whenever the title character starts really losing it in Jackrabbit Messiah by Geoph Essex, the voice he usually hears starts getting printed in smaller and smaller (and fainter) text. When he's totally lost his mind (leading up to The Climax), the dialogue from the less helpful voices in his head is printed in text that gradually fades in and out (in shades of gray) from the beginning to the end of each paragraph. It's described in the narration as a kind of schizophrenic "Doppler" effect, and the medium painting does a pretty effective job of demonstrating it.
The Reader (2016) has several pages with dirty fingerprints on them, a few with notes in the margins, and one notable paragraph that is entirely blotted out. It's one of the first hints that the book you're reading is an excerpt of the book in the story.