Vanity publishers are companies that will essentially publish almost anything a would-be author has written, regardless of quality or potential market. Obviously, most of these books never sell, but some people just really want to see their name in print (hence the name "vanity" press).
When a traditional publisher accepts a book for publication, it pays all the expenses related to publication in return for a certain percentage of the proceeds. The publisher is betting that the book will earn them more than it costs them to produce, which is why they're only interested in books that are likely to sell well. A vanity press, on the other hand, has the author foot the bill, which allows them to publish practically anything and still make a profit. This will often lead to fairly large expenses on the part of the writer, and is why many vanity presses tend to be dishonest about sales possibilities in order to get people to pay.
Unfortunately, the actual books produced by vanity presses are often all but impossible to sell for a number of reasons.
Most stores won't carry them. Bookstores prefer to deal with legitimate publishers, as vanity presses have a terrible reputation for stiffing bookstores.
Occasionally (very occasionally) a vanity published book can break out and end up being published by a legitimate publishing company. This happened with the children's book series The Fairy Chronicles. It originally cost a lot and had only 32 pages (due to its small typeface), with no color and no illustrations. Once moved to a new publisher, it had vibrant color, many illustrations, and more pages (with a larger, more appropriately sized font).
Interestingly, many vanity presses support Amazon.com's "Search Inside the Book" feature and other book searching sites. While this can help readers find the rare gem in the rough, it also allows them to easily see why so many vanity published books just plain suck.
It's worth noting that there are differences between a vanity press and a self-publisher. In self-publishing, the writer takes on the duties of editor and formatter himself, simply contracting with a printing firm to produce the physical book. Naturally, for similar reasons, many (but not all) self-published books also suck. Some do not, and some have to be self-published even though they're high quality and well written, because they wouldn't sell in the real world, e.g. the history of a corporation. (Would you be interested in the corporate history of BB&T Bank? Well, that bank has a history of itself, well written and professionally produced, in the lobby of every branch for customers to read. Even though the book is well done, seriously, nobody in the general public would be interested in buying it.)
Self-publishing may also be used for master's and doctoral dissertations, if the university expects them to be bound, and for writers whose texts are not in the dominant language of the country they're publishing in. Self-publishing is also very common in the developing world, where in some countries (India, most notably) more books are self-published than are published by commercial publishers. Online self-publishing has also been taking off as well, with sites such as Lulu letting any aspiring author submit his manuscript, choose the printing and binding options, and printing and delivering them on demand to anyone who buys the book.
Since vanity published books are almost by definition obscure, pretty much all examples will be obscure as well:
A Distant Soil, but for a different reason - it was originally published by Richard Pini of ElfQuest. However, author Coleen Doran severed the contract after nine issues because of the Executive Meddling. (Wherein dialogue, art, and cover changes were made without her approval, and she even stated in one of her memos that they even wanted to take her off the project. Pini has allegedly also tried to get the rights to it, too.)
In one of the craziest examples, in 2008, Oklahoma County Commissioner Brent Rinehart created a bizarre 16-page comic detailing his vehement opposition to homosexuality and painting his opponents as being inspired by Satan, and then distributed copies to his constituents in an attempt to convince them to re-elect him. He ended up losing the primary and facing felony charges relating to his 2004 campaign.
The first few books of The Cross Time Engineer series were published by Baen Books, but the later novels are entirely self published.
Another Hope is a Star WarsFan Fic by Lori Jareo in which all the main characters die in the first episode and the author's Mary SueAuthor Avatar takes over. Also, the Star Wars Galaxy now apparently possess a Starfleet. When Jareo, in a move that must have taken balls of steel, had the story vanity-published and put it up for sale via mainstream channels like Amazon.com (claiming that it was okay do so because only her family knew it was there), George Lucas' lawyers wept tears of burning sulfur.
The Adventures of Archie Reynolds. Horrible dialog, Beige Prose galore, and very repetitive writing. There's dozens of examples of Archie thinking that he's going to do so something, then saying out loud that he's going to do something, and then actually doing it; all in the exact same words. (e.g. Archie wants to get back at a girl who cracked an egg over his head. He sees her swimming pool and thinks to throw her in there. He then says out loud that he should throw her in the pool. He then throws her in the pool.) There's also a gang of bullies who talk like pirates for no reason, and a scene in which the characters speculate on the purpose of a ladder and come to the conclusion that it is for climbing up or down. Gee, who would have guessed. The author attempted to promote his book by using multiple accounts on Amazon.com to write nearly identical glowing reviews. It was obvious from clicking each screenname that the accounts were created just to praise that book. He'd even tried the same stunt in other places as well.
The Fairy Chronicles was originally vanity published by PublishAmerica, but its author was able to promote it well enough that a legitimate publisher picked it up and gave it much better treatment, adding vibrant color illustrations, a beautiful cover, and many overall improvements. The fact that the books are decently written helped, but the author's own ability to actually market her (originally overpriced) work is probably what pushed it into the mainstream.
In the same mold (vanity published book gets picked up by conventional publisher and it achieves mainstream success): James Redfield's The Celestine Prophecy. Redfield sold over 100,000 copies of the book out of the trunk of his car before Warner Books picked it up. The rest, as they say, is history.
For the curious, you can find a list of other well known books which were self-published and became prominent here. The list does contain flaws, however.
Some of the worse prose of all time is in The Shadow Mouse of Everjade. If you look it up on Amazon and read an excerpt, you will get some idea of the quality.
Wild Animus was vanity published, and then, for a time, sent to anyone who wanted it, free of charge. The book itself was generally considered to be worth less than the $0 most readers spent on it.
The Great American Parade, a novel which attempts at political satire by retired English professor Robert Burrows, was vanity published in 2002. Since then it's been called "the worst novel ever published in the English language" by a Washington post review. The story deals with George W. Bush organizing a huge parade to thank all the evil corporate robber barons who helped him get into office; somehow hardly anyone in America notices, except for a plucky band of college students who set out to single-handedly stop the parade, end the war in Iraq, and undo the Bush tax cuts. It features such brilliant dialog as this gem (spoken by a character immediately after witnessing the events of 9/11): "What an almost unimaginable tragedy! It will take a great deal of unity and hard work to recover from this crippling blow!"
Maradonia Saga: Once upon a time, a girl named Gloria Tesch wrote a woefully generic young adult fantasy novel about a Gary-Stu and Mary-Sue who discover a magical land adjacent to the US, à laNarnia, fulfill a prophecy, turn out to be Chosen Ones, and fight against an "Evil Empire" (yes, that is what it is called; in spite of the fact that a reading of the first chapter reveals that isn't actually an empire anyway). Random words being italicized or in quotation marks for no fucking reason does not help. Her parents told her it was brilliant, published it, and the girl has since developed an ego the size of a planet; proclaiming herself the world's youngest published author (which she isn't), dismissing the most meager negative criticism as the work of "haters", and is under the impression that a Maradonia movie and amusement park are on the way. Amazon.com and other such websites are full of reviews written by the girl, her parents and her friends in which they relentlessly praise the series.
E. Lynn Harris self-published his first book, and by tireless promotional touring sold a lot of copies and got it picked up by a regular publisher. Many of his subsequent books have been bestsellers.
One of the most notorious examples of vanity publishing is Night Travels of the Elven Vampire by LaVern Ross; originally thought to have been a parody of vanity publishing, a la Atlanta Nights. Once discovered to have been a serious attempt at writing; it became the subject of multiple scathing reviews, some of them brilliantly hilarious. Notorious for its over-the-top Mary Sue lead, laughably bad language, and bizarre graphic sex scenes; it generated at least two Internet memes. Eventually dropped by Amazon.com, a nearly identical "re-imagined" version, Eternity of Blood, was subsequently vanity-published; written by Ross under the pen name Valena Graham.
A book exists called How to Good-bye Depression: If you constrict anus 100 times everyday. Malarkey? or Effective Way? by Hiroyuki Nishigaki and can be found on Amazon. Once you've finished snickering; it is published by "Writers Club" and iUniverse.com, and is largely made up of the author explaining his theories relating to how depression can be cured on newsgroups in 1999 and 2000, along with people reacting in various ways. The book is perhaps the best example since Zero Wing of the results of making literal translations of Japanese to English, with sentences like: "Besides shooting out a big blank from your buttock, you can feel as if your root chakra leaked sweet hot mucus" (we'll give you another five minutes to stop snickering again). At the end of the book, the author thanks the reader for taking the time to read his book in spite of his English being so bad. Well, at least he's humble, which is more than we can say in regards to most of the authors who wrote the pieces of nonsense listed on this page.
Another example of a previously self-published work picked up by a legitimate publisher: Gollancz has paid a six-figure sum to acquire the Stonewylde series by Kit Berry.
Kenneth Eng is proof-positive that white supremacists aren't the only insane racist bunch around. A self-proclaimed Asian supremacist who claimed credit for inciting the Virginia Tech massacre, Kenneth Eng published obvious Flame Bait articles in the California newspaper Asian Week titled "Why I Hate Black People" and "Why I Hate White People." Once word of this got out to the mainstream media, he used the exposure to plug his vanity-published science-fiction book! Said book, Dragons Lexicon Triumvirate, is pretty much awful, but he's written glowing five-star reviews of it on Amazon, while pretending to be someone else. He even writes reviews of other books just to mention it. His review of The War of the Worlds amounted to: "This book is good, go read Dragons: Lexicon Triumvirate." He's also stooped to sock-puppet antics on various literary fora, bringing up a topic and then using it to plug his book.
Paul Arthur Trainer (variously known as Paul Trainer, Arthur Trainer, and Paul Arthur Trainer), author of Clown (in which the author's Mary Sue spends entire chapters plugging his other books, and Bill Gates is killed by the titular psychopath whilst living in a house "made entirely of brick"), Witch (in which the titular Big Bad is actually aided by a flying monkey), and Life Flash (in which a woman threatens to divorce her husband if he has ever seen a bear) has developed something of a cult following among small-press horror writers and fans, who have been known to read his books aloud at conventions, to maximum comedic effect.
"Visit the dark bowels of death as one victim after another will lead you to believe there is a reason for revenge; cold, hard, blood-curdling revenge. Who is the killer? And are you sure? It could be someone you least expect. Old Tavern No. Nine, set deep in the Santa Cruz hills, will never be the same and neither will you?"
John Harrigan's The Professor and the Dominatrix, published by PublishAmerica, was apparently sent out by the author to some atheist groups at its release. It was a murder mystery featuring sex and violence, which was hoped to draw the reader in and then lead them to question their religious beliefs more closely. One member of a receiving group decided to review it and put her review online. Unfortunately, she did not particularly care for the book. According to the review, much of it was basically a long Author Tract, and the main character was a blatant Mary Sue, to the point that he wasn't just an outspoken atheist like the author, but even had the exact same day job too (professor of psychology), and a mustache. The author responded to the criticisms by, among other things, pointing out the favorable review the writer of the foreword gave it, similar to what the one non-deleted Amazon review did (the remaining review mentions other, critical reviews that were presumably deleted; it is implied they were sock puppets). It left many readers on the Pharyngula blog thinking or hoping the book was an elaborate joke. (Note, the remaining Amazon review is not from a sock puppet; it is a "real name" account for someone other than the author or foreword writer. It was the reviewer's only review though, so it seems to be purpose built).
Harry Potter's muggle's guide to magic must fall under this category. There's no other way to describe this 'dictionary' of the Harry Potter books that was published well before the series concluded. It's rife with misspellings ("wizardu books"?) and inaccuracies — apparently Draco Malfoy's father is named "Dracus", Dumbledore's first name is "Albert", and the Weasleys' car was a Flying Ford Angelica. The writing is also incomprehensible and manages to confuse the plots of the second and third books in the series. The art is just as bad; while Hermione wearing glasses is a mild oversight, making Hagrid into a four-foot-tall lumberjack and giving Mad-Eye Moody green skin is much less forgivable. At least we may all take comfort in the fact that the book is out of print.
The National Library of Poetry, anyone? Sure, you don't have to pay anything to get published...but you know they expect you to buy the book, and pay to travel to the conference where your poem will allegedly be read, and so on and so forth. People, including Dave Barry, have gotten in on the attempts to send something that's actually bad enough that they'll refuse to publish it; so far, no dice.
Orbit has bought the rights to the previously self-published six book series The Riyria Revelations by Michael J. Sullivan and will re-release it as a trilogy.
Lundon's Bridge and the Three Keys, published in 2011, is a children's fantasy novel intended as the first in a franchise of five books and their film adaptations, suggesting vanity filmmaking as well as publishing. It came to public attention only when Paris Jackson (Michael's daughter) was announced as playing the lead in the movie — she even appears on the cover — and the book is only available through the official website and Amazon.com. It's a loopy one: When her husband and daughter are seemingly killed by "The Decayed Sea" (Water Is Air is badly abused in this book), the jellyfish queen of the ocean kidnaps a human scientist, using his form to assume a human shape and turn kidnapped children into a half-human, half-insect army to destroy humanity for its pollution. Her plan hinges on destroying the belief in the heart of the scientist's 16-year-old daughter Lundon, who ultimately must save the day with help (a lot of help) from a dolphin that can turn into a human, a shapeshifting and fire-breathing seahorse, and a surfer friend who gets turned into a dragonfly. Supposedly this was in the planning stages for thirty-plus years; the movie is currently in Development Hell.
In-universe example in Foucaults Pendulum: The three main characters, who all work at a vanity press that's been getting a lot of manuscripts from occultists and conspiracy crackpots, decide to one-up them all by creating the Ultimate Conspiracy Theory. Things then go horribly right.
In a twist, the not-terribly-obscure, not-at-all vanity published How NOT to Write a Novel is a how-to guide for writers taking the form of how to remain completely unpublishable. In addition to providing tips on how to make your protagonist insufferable, your plot horrid, and how to make sure no editor talks to an unprofessional boor such as yourself, it contains a truly sincere and serious warning about this business practice. The vanity publisher in the book is even called Fuxom and Snickers.
The nonsensical plot and complete lack of understanding of biology present in Victoria Foyt's Save The Pearls might have gone unnoticed entirely, but for the fact that the book gathered extremely negative attention for its clumsy and insensitive handling of the Persecution Flip that serves as its main premise: a dystopian future where minority whites are discriminated against by a black majority, because higher melanin counts were less likely to get skin cancer when the Earth was bombarded with increased UV radiation. In the book it's a plot point that "Pearls" (whites) cover themselves in dark makeup to fit in... meaning blackface. The book also had several promotional videos done, with actors in blackface. With the author point-blank refusing to acknowledge there being anything remotely problematic about this, deleting all negative criticism of the topic on her Facebook page, and having apparently fabricated the majority of her own book reviews, it went from unheard of to infamous almost overnight, generally turning into Bile Fascination as the depths of the novel's ignorance and insensitivity were more fully explored.
Vanity pressings are the audio counterpart to vanity publishing. These could be something as benign as an unsigned band making a vinyl recording (essentially self-publishing with sales at shows) on up to companies that would write and record songs using the finest in talent and audio equipment around the authors lyrics for a fee. Some of these have become cult favorites thanks to blogs like WFMU's 365 Days Project.
An in-universe example happens in one episode of SpongeBob SquarePants. Patrick writes a song and sends it to a music company, who has to make the song since they already used the money that came with it. The song ends up killing the musicians that had to play it.