The differences between books and the movies made from them
The differences between books and films are not a matter of taste or budget: 5 things change in every crossing because the two forms are built differently, and no adaptation has ever kept all 5. A film cannot hold interiority, it cannot hold the reader's clock, it cannot carry every subplot, it cannot use a narrator the way prose does, and it almost never keeps the ending untouched. Everything else that changes is negotiable. These 5 are structural, and they are the reason a reader walking out of the cinema says the film was not the book without being able to name what was missing.
| What the film loses | What it substitutes |
|---|---|
| Interiority | Behaviour, invented company, voice-over |
| The reader's clock | Fixed running time, cutting, ellipsis |
| Subplot | Compression into a single line of action |
| The narrator | A frame device, or nobody at all |
| The ending | Resolution the audience will accept |
Interiority: the thought that has no picture
Interiority is the first loss, because a camera records surfaces and a novel records the inside of a head. Prose can spend a page on what someone decided not to say. Film has 3 substitutes and each one costs something. It can invent company, as Henry Selick's Coraline of 2009 does by adding a boy who is not in Neil Gaiman's 2002 novella, so a girl who thinks alone for a whole book now has someone to think out loud at. It can use voice-over, as David Fincher's Fight Club of 1999 does with Chuck Palahniuk's 1996 novel, which works but converts a private mind into a performance aimed at the audience. It can play the thought as behaviour and trust the actor, which is the hardest option and the one that ages best.
The problem sharpens when the interior voice is not human. Shelby Van Pelt's 2022 novel Remarkably Bright Creatures gives chapters to a captive giant Pacific octopus. Any adaptation has to decide whether the animal speaks, thinks in captions or simply watches, and all 3 answers are large departures from a book whose charm is the animal's private commentary.
Time: the reader controls the clock and the viewer does not
Time is the second loss, because a reader sets the pace and a viewer is handed one. A novel can put 17 years between 2 chapters and the reader absorbs it in a sentence, which is exactly what Peter Jackson's The Lord of the Rings: The Fellowship of the Ring of 2001 could not do: the 17-year wait between the party and Frodo's departure is gone, because a film cannot keep a protagonist idle for that long without losing the thread.
Interleaved timelines suffer the same pressure. Stephen King's It, published in 1986, cuts constantly between the children in the 1950s and the adults nearly 3 decades later, so that each period comments on the other on the same page. Andy Muschietti's films separate them completely, into It in 2017 and It Chapter Two in 2019. Both films are coherent. The mechanism that made the novel work, memory intruding mid-scene, is not in either of them.
Subplot: the strand that pays for the running time
Subplot is the third loss, and it is the one that buys everything else. A 400-page novel carries 3 or 4 strands; a 2-hour film funds roughly 1. Steven Spielberg's Jaws of 1975 drops both the affair and the organised-crime strand that run through Peter Benchley's 1974 novel, and the removal is why the film reads as clean. Robert Zemeckis's Forrest Gump of 1994 goes further, discarding most of the episodes in Winston Groom's 1986 novel and keeping a shape the book does not really have.
Cutting a strand is rarely just subtraction. Take out the subplot and the characters who lived in it lose their reason to be there, so they are merged, reassigned or deleted, and the main line quietly absorbs their functions. That is how an adaptation ends up with a character who behaves in a way readers do not recognise while every scene they appear in is technically in the book.
The narrator: a voice with no body on screen
The narrator is the fourth loss, and the least discussed. Prose narration is a person, positioned somewhere, with reasons to shape what they tell. Film has no default equivalent, so adaptations either invent a reason for the voice or drop it. Baz Luhrmann's The Great Gatsby of 2013 invents an entire frame, placing Nick Carraway in a sanatorium writing the account, which manufactures a purpose for narration that F. Scott Fitzgerald's 1925 novel simply assumes.
Nested narrators fare worse. Mary Shelley's Frankenstein of 1818 arrives through an explorer's letters, then Victor's account, then the creature's own testimony, and the layering is the argument: the reader hears the monster explain himself. James Whale's 1931 film removes all 3 layers and the creature's speech with them. Kenneth Branagh's 1994 version restores the Arctic frame and gives the creature language back, and the story changes category as a result.
The ending: the last thing to be renegotiated, and the first thing readers check
The ending is the fifth loss, and it is renegotiated more often than any other element because an audience leaving a cinema is a commercial event in a way a reader closing a book is not.
King's 1977 novel destroys the hotel: the boiler goes up, and the father recovers enough of himself at the end to matter.
Kubrick's 1980 film leaves the hotel standing and freezes the father in the maze. The building wins, and no recovery is offered.
Reversals run in both directions. Steven Spielberg's Jurassic Park of 1993 spares John Hammond, whom Michael Crichton's 1990 novel does not, converting a fable about consequences into a rescue. Nick Cassavetes's My Sister's Keeper of 2009 turns over the outcome of Jodi Picoult's 2004 novel, which readers noticed immediately and argued about for years. Checking the ending is the first thing a reader does after seeing the film, and film-makers know it.