Think back to the last time you told someone a story of something that happened to you. Think about how you described it, the language you used, and what parts of the story you emphasized.
Chances are you cut to the chase quickly, or at least mentioned only the details important to building up the story, and then you described the events in casual language. You didn't describe it the way a book is written.
Yet, virtually every single first-person narrative in existence in any novel is dramatically written, spends a lot of time on not just events important to the story, but also ones that build character, or even events not really important at all. Events are described in the same amount of detail that they are in third-person narratives. The narrator often uses a higher and more formal level of English than their own dialogue. As far as structure goes, it's essentially the same as a third-person limited narrative, except it happens to be in first-person.
There's several reasons for this. For one, a first-person narrative allows readers to get into the main character's head in a way that a third-person narrative might not. It allows The Protagonist to describe things bluntly or colorfully in a way that might look strange coming from a third-person narrator. (Although the Lemony Narrator, by definition, does so all the time.) It allows for a story that feels more "human", but at the same time, due to this trope, still reads like a novel and contains the same level of excitement.
It also allows for a more exciting story. When's the last time you heard someone describe an experience in as much detail as your favorite book? If they did, it would probably be a more exciting story... but also a much longer one. This way, you get the best of both worlds: a story with the depth of storytelling of a novel, but the humanness of its protagonist infused into the narrative itself.
It can stretch plausibility if you think about it, and more so when the narrator is very young or uneducated, but hey, that's why we have the Literary Agent Hypothesis and the MST3K Mantra. This is one of those Acceptable Breaks from Reality that's so commonplace that we tend not to notice it.
Sometimes this is justified in-story, when the story claims to be a book written by the character who is the narrator.
Sometimes writers try to avoid having the narrator sound too much like a narrator speaking the King's English, by having them write in an informal, more casual dialect. However, there's usually one consistency across all first-person novels: The events in the story are described in more detail than an ordinary person casually relating a story would likely ever give.
Owing to the ubiquity of this trope, only unusual variants or subversions will be listed:
- "The Chymist" by Thomas Ligotti is a justified variant of this trope: The character is an Insufferable Genius with an obvious penchant towards self-indulgent soliloquy, and hence speaks rather vividly. It's even lampshaded several times by the narrator himself. His companion lampshades it as well, although since she's in effect us, we only hear his responses to her.
- Another justified example would be in Wuthering Heights, where Lockwood, the initial narrator, is a bit of a prat and the kind of guy who would be prone to this sort of thing. Then when Nelly tells most of the story, he specifically requests it be told like this.
- The first-person narrator in the novel The Lacuna writes like a novelist because he actually is a novelist.
- In The Catcher in the Rye, the narrator, Holden Caulfield, accurately represented the colloquial teenage dialect of the era.
- As I Lay Dying by William Faulkner features stream-of-consciousness narration from people that include children, the dying and the insane.
- Room, by Emma Donoghue, is told from the perspective of a five-year-old boy, Jack; while it's not exactly the way a five-year-old would speak and write (possibly justified, given Jack's upbringing), it's immediately very clear from the writing and syntax that it's a child speaking.
- Averted in Coyote Kings of the Space-Age Bachelor Pad. The book is narrated from several first person viewpoints, and only some of them come across as literary narration; others come across as the narrator just riffing, stream-of-consciousness.
- Tom from King Dork, being a modern-day Catcher, also avoids the "King's English" style of narration.
- Riddley Walker by Russell Hoban is a post-apocalyptic novel set in what used to be the English county of Kent. Riddley narrates the entire book in something like a phonetic transliteration of a Kentish accent. Example: "We ben the Puter Leat we had the woal worl in our mynd and we had worls beyont this in our mynd we programmit pas the sarvering gallack seas."
- The Perks of Being a Wallflower is another aversion of this.
- Mark Gatiss' Lucifer Box novels play with this trope. The narrator comes across as a bit of a rambling hack, seemingly trying to play this trope and failing miserably, ending up with a style something like a very eloquent man relating his life story orally in his Smoky Gentlemen's Club (which he does indeed like doing at every opportunity). Occasionally overlaps with First-Person Smartass.
- Flowers for Algernon, about a man with learning difficulties who undergoes a medical procedure to turn himself into a genius, plays with this. The first-person writing starts off poorly spelled and simplistic but dramatically improves as the procedure begins to show effects.
- The Curious Incident of the Dog in the Night-time is narrated by a teenager with an autistic spectrum disorder, thereby averting the tendency of first-person narrators to write in a polished, literary style, while also justifying the level of detail.
- The Crimes of the Sarahs by Kristen Tracy kind of plays with this, in that it has a lot of the random thoughts that someone would have as opposed to simply being about the main character's story line.
- Mark Twain's Adventures of Huckleberry Finn was criticized for (among other things) the hero narrating the way an uneducated 14-year-old from the Deep South in the 1860s would talk. But that don't matter none.
- Chuck Palahniuk says his bare, stripped down Signature Style comes from trying to emulate how people naturally tell stories.
- In Iain M. Banks's Feersum Endjinn, the sections narrated by Bascule make heavy use of phonetic spellings and Letters 2 Numbers. Wich u mite thnk is vry kool, or just 2 anoyin 4 wurdz.
- How I Met Your Mother: Ted's narration often displays a rather haphazard style (especially in the first three seasons), occasionally dropping random spoilers and explanations into the story instead of working them into the plot properly (e.g., pausing the action in "Okay Awesome" to say "Oh I forgot! This is important: your Uncle Marshall just had a temporary filling put in that afternoon" right before it plays a part in the story.) He also tends to meander around at random: for example, in "Showdown", in the middle of Past Ted's best man speech at Marshall and Lily's wedding, Future!Ted suddenly interjects with "Oh wait! I forgot to tell you guys what happened to Uncle Barney!" and spends the rest of the episode showing a completely unrelated scene from a different storyline, and doesn't come around to telling the wedding story until the next episode.
- In Tosca Lees Demon: A Memoir it is justified because the narrator is both an editor and a novelist; the story is both his larger story and implied to be the book he is writing in-universe.
- Oddly, both justified and averted in the first book of Megan Whalen Turner's Queen's Thief series in which the story turns out to be a book written by the scholarly and book-obsessed narrator in a much less scholarly style. Possibly justified or unjustified when the same thing occurs in the fourth book. (The narrator, who is not the same as in the first book, is telling the story verbally, not writing it down, but he's a rather sensitive and detail-oriented guy).
- Fifth Business by Robertson Davies is a particularly egregious case. Elaborate writing aside, the first person narration comes off as a bit odd because the entire story is framed as a letter from the main character to the headmaster of the school that he works at. Said "letter" happens to be around 300 pages long, and it describes around forty years of the protagonist's life in intimate detail, including gratuitously long passages describing his thoughts about obscure Catholic saints. When was the last time someone wrote their autobiography as a letter to a friend? Hell, how many envelopes can fit a 300-page letter?
- J.M. Coetzee's Age of Iron is also supposedly a single letter from a dying woman to her daughter.
- A novel by Mariama Ba, which is supposedly a letter from a woman to her friend, is actually titled Une si longue lettre ("Such a Long Letter").
- Most of the stories in The Thirteen Problems by Agatha Christie, which are supposedly being told by different members of Miss Marple's circle. The exceptions are the last three: one is narrated by Mrs Bantry (see page quote), and mostly consists of the others asking questions in order to get any detail at all; one is narrated by a Brainless Beauty who needs a lot of help to get the story straight; and the last simply doesn't maintain the framing device.
- Forward the Mage toys with this, as the story is narrated by a series of lice who write like very old-fashioned novelists of varying skill levels. This trope is probably why the lice exist in the first place: no one wants to read an entire book in Zulkeh's voice.
- Dangerous Liaisons is an epistolary novel where the characters show markedly distinct styles and much of its literary worth comes from that fact. Marquise de Merteuil is florid and exuberant in her writing, often addressing her reader directly, while vicomte de Valmont is drier and more procedural, with a tendency to Exact Words. Both the young people repeat themselves a great deal and have a poor vocabulary, while Madame de Tourvel writes convoluted, rambling sentences. When Valmont starts to dictate Cecile's letters the difference is obvious.
- Pale Fire by Vladimir Nabokov is a first-person narrative disguised as a critical edition of a poem: the narrator is the editor, not the poet, who is dead. The "editor" slips his narrative into the preface and annotations, and it becomes increasingly clear that he resents the poet for not including his narrative into the poem itself. Then it becomes clear that the editor's an Unreliable Narrator and that the "true" narrative is lurking on an even deeper level...except that there might be an even more "true" narrative lurking beneath that one. And so on.
- Money by Martin Amis is narrated by an ignorant, boorish, drunken (and sometimes amnesiac) slob, John Self, apparently as a suicide note. It's a very long suicide note, and for someone supposedly near illiterate, full of beautiful, if slightly strained, imagery.
- Justified in the 6th Thursday Next Book, One of our Thursdays is Missing, as the first person narrator is an in-universe first person narrator, having an adventure in between being read in her own in-universe book. If that makes sense.
- Dan Simmons has a fondness of writing parts of his books as journal entries from people who are going insane or dying. It happens part way through Hyperion and near the end of The Terror.
- The novel Confessions of Felix Krull is a rather extreme case, as the narcissistic narrator is also very much in love with his own writing (in the very first sentence of the book he notes that he is penning his memoirs "in clean and pleasant handwriting") and often takes pain to speak as if he was writing. For instance when recording his first conversation with Professor Kuckuck he says that he chose a certain word out of pure excitement and because he wished to discuss the subject formally and in "book German".
- Downplayed in the Inside Out Novelization Driven by Emotions, in which each of Riley's five emotions recounts the plot of the film as they experienced it in turn. Because the emotions have vastly different personalities and focus on certain issues above others by nature, they write rather casually, speeding through certain events and lingering on others (occasionally explaining why they do what they do), and are light on elaborate descriptions. (This keeps the book from becoming tediously repetitious.)
- The Kingkiller Chronicle is framed as Kvothe's extremely articulate dictation to the Chronicler, which he forbids him from revising or condensing. Lampshaded when he takes a night to collect his thoughts before beginning, because "A real story takes time to prepare," after all.
- The Hunger Games is for the most part a subversion. Lots of jokes have been made about how it's written largely in sentence fragments due to its Beige Prose style. The story is told in first person present narration through the eyes of a sixteen-year-old girl being put through all kinds of trauma.