BINGO!
See also
I am Legend as it totally changes the theme of the book (he becomes a monster himself) and Minority Report.
Oh God Minority Report was a 2 hour rape of the Phillip K. Dick. The biggest difference is that in the movie Tom Cruise finds personal happiness and closes pre-crime. In the book, the character commits the murder as predicted. He sacrifices himself in order to save pre-crime.
You know, the motivation of the main character is the polar opposite of book it is based upon.
I hated the movie adaptation of “The Shining” - but loved the book.
Also “The Stand” and “the Firestarter” were pretty bad.
Hitchhiker’s Guide comes to mind. The movie was embarassing.
“A Wrinkle in Time?” One of my favorite books ever. The movie actually made me cry because it was so horrifyingly bad.
Naw, it still sucked.
There was a MOVIE? 
For anybody on here who says it sucked, I’m sure I could find 2 people elsewhere who, like myself, liked it.
The Stand was fairly awful but it wasn’t made into a movie. It was a miniseries.
The 1995 film version of the Scarlet Letter is usually considered the classic case of a hack screenwriter trying to “improve” a classic work of fiction.
For those of you who slept through English class, Hawthorne wrote the story so that it intentionally reflected a Puritan mindset - Hester Prynne, a devout Puritan, accepts the communities’ punishment of her, in fact genuinely believes that by giving into lust, she is forever tainted by sin, and that her daughter (born out of wedlock) is possibly tainted as well. She accepts whole-heartedly the notion that she brought her troubles on herself. The narrative arc of the story is more concerned with whether or not Reverend Dimmesdale (whom Hester had “carnal relations” with) will confess his own sin publically.
But of course, a modern day (and likely Demi Moore herself) realized how foolish all this sounded, so they rewrote the character of Hester as an age-of-Oprah style “empowered WOMYN” who rebels against the hypocrisy of the religious community and holds her head up high in the face of OPPRESSION. To further drive home the point, sub-plots concerning a quasi-lesbian slave, and a “Native American” tribe are tossed in. Liberally sprinkled with titty shots & scenes of “wontonly lustful” groping.
There is no way 3D is going to bring The Great Gatsby to life. So I’m preemptively hating it.
“So we beat on, boats against the current, borne back ceaselessly into the past…and it’s coming right at us!”
I’m surprised no one has mentioned The DaVinci Code.
I loved this book. It was one of those books that I couldn’t put down - it was so packed with action that I just had to read one more page to find out what happens next.
So I remember thinking that if a movie has to leave stuff out and condense the story even more, then WOW, it’s going to be a dizzying, non-stop, thrill ride. But somehow Ron Howard managed to make it plodding and boring. I couldn’t believe it.
The Grinch (How the Grinch Stole Christmas). The Whos had a key party, for the love of pete. I wanted to punch that movie in the cock.
The Neverending Story. Twice.
De Gustibus… and all, but the reason I didn’t list it was that I don’t think of The DaVinci Code as a good book.
More examples
**Nightflyers
Murders in the Rue Morgue** (several times over)
**Off on a Comet
Robur the Conqueror
In Search of the Castaways
The Time Machine
A Connecticut Yankee in King Arthur’s Court** – many, many times over. A pet peeve of mine, as I think you could get a wonderful film out of this.
The Food of the Gods (twice at least)
War of the Worlds many times over
**Nightfall
The Tenth Victim
The Running Man
Immortality, Inc./Immortality Delivered** (filmed as Freejack)
Brave New World (the first time, anyway)
The Terrornauts (really awful SF film written by John Brunner, based on a Murray Leinster story, The Wailing Asteroid. I’ve never read it, but it can’t have been anywhere near as bad as the film. But – Brunner? Leinster? Two stars of SF worked on it, and it came out this bad?
If there is ever an award for this category of film, it will be called The Troopie.
The award would be in the form of an Oscar-style figuring presenting the head of Paul Verhoeven on a platter.
Most of the ones I thought of are taken, except Casino Royale (1967).
I’ve read the book and seen the movie and liked both, although the movie has only a passing resemblance to the book, so I try to keep them separated in my mind. But the movie has a bunch of gratuitous violence and explosions, a little gratuitous nudity, some decent special effects, and NPH as a telepath in a Nazi uniform. What’s not to like?
I think “anything by Stephen King” is the winner here.
It’s a shame, since he tells such good stories. But I think it’s because he tells them so well, the reader has his/her own mind movie, and nothing on film could do it justice.
Hmmmm…Carrie, The Body, Misery, Shawshank Redemption and The Green Mile were not so bad.