Honestly, it'd be easier to say which books have GOOD adaptations, since the norm is poor adaptations and it's hard to choose which one is the worst since so many suck in different ways.
Going to have to second The Dark Tower. To say it was a letdown is nowhere near enough.
The Witcher show starts off pretty well but quickly gets worse and worse. That's probably my number two.
I also thought The Hitchhiker's Guide to the Galaxy movie was pretty disappointing, though not the worst of the worst.
I could probably think of a lot more if I browsed my book collection. Rare is the adaptation that meets the quality of the book. That would be a much shorter list. If we were looking at that question, the first movie that comes to mind is The Amityville Horror because that book had some of the worst writing that I have ever subjected myself to.
Not seeing Ready Player One listed here. There were some choices made in that movie that might seem fine to someone who hasn't read the book, but the huge number of absolutely unnecessary discrepancies was just gross.
Pretty much every movie based on a Crichton novel except the first Jurassic Park and the original 1971 adaptation of The Andromeda Strain. Every other one has been awful (including The Lost World which is so far from the book it shouldn't even get to be called "based on").
Edit: After sleeping on it, I don't know if the movie adaptations are objectively awful or if I was just unimpressed because I read the novel first for all of them.
Wwz. Still salty. It would have been spectacular if done along the same line as Supervolcano - the after fact interviews intercut with events as they happened was practically made to order for it - instead we get another shitty paint by numbers grab.
World War Z is barely at all like the book, and does a lot of really fucking stupid shit instead of having some of the really fucking cool shit from the book.
Like instead of a blind martial arts master surviving the zombies, we get to see one of the main characters slip on a ramp and break his neck. 😬
I still hate how Max Brooks said "Now, it's a little unlike my book, but still good in it's own right!" Because it wasn't.
Dark Tower - But I don't think it can be done. I think the reason a lot of Stephen King's adaptations fail as movies is because his books spend a lot time describing his character's inner monologue.
Ender's Game - I was so excited for this movie. But if you are a fan of the books then you saw a lot of discrepancies between the movie and the book. So it ended up being a decent general sci-fi movie.
Percy Jackson and the Olympians. Especially the second movie, Sea of Monsters.
Thank goodness the TV show is coming in December. Rick Riordan, the author, has personally been overseeing the production. I have high confidence the tv series will be much closer to the books. Hopefully this will do well enough that future seasons will be funded and we’ll get seasons that adapt the rest of the books.
Starship Troopers. The book is great, but the movie is like if someone wrote a short summary of the cliffs notes of the book. I guess they both had bugs.
Put a list of Ursula Le Guin works on a wall and throw a dart at one of them. Don't know which one you threw a dart at? That's okay, because absolutely none of them have gotten good adaptations.
The only exception, extremely ironically given I'm saying this, is Tales of Earthsea. The first half is alright but I guess they lost their train of thought during the second act (their words not mine) and it became a Legend of Zelda story. Still not terrible though, I can't understand why people hate on it when the same people love Ponyo.
Battlefield Earth was my favorite book as a young teenager. Ignoring everything else about the author (which I didn't know at the time), I thought the book was brilliant (especially the first half). It touched my imagination in a way no other book had before, and I must have read it about a dozen times.
I seem to recall the book cover saying that a major motion picture was coming out soon, but I guess time is relative. For me it was about eighteen years (which was more than half my life at the time) before the movie actually came out, and that seemed like an eternity.
I wish I could say it was worth the wait. The movie was horrible -- it had bad acting, a bad script, and couldn't carry the book in only two hours.
It currently has a 3% tomatometer score at Rotten Tomatoes and a 2.5/10 at IMDB. The movie also won Worst Picture of the Decade at the 2010 Razzie Awards.
I hated the two made for TV Terry Pratchett adaptations of Colour of Magic and Going Postal. Like, they pissed me off so hard I couldn't sleep. Particularly Going Postal (my favorite Pratchett book), they couldn't have missed the point of it any harder even if they tried.
The first season of the TV series is a banger, but the subsequent seasons suffer from a decline in quality. Also, the series finale is just so disappointing compared to the ending of Gaiman's novel.
Are you referring to the Golden Compass movie or series? The movie was trash, but I thought the TV series they've been doing has been pretty good.
For me Ender's game was a massive disappointment. I also didn't like the hobbit trilogy. Huge fan of LOTR, but the hobbit movies just didn't do it for me.
I don't know if it's the worst, but I am very disappointed with the movie adaptation of Mortal Engines. The series has such a rich world to explore and very good plot points that would have been amazing to see on the big screen.
The movie ruined any possibility to see a sequel or even a reboot in a very long time (similar to what happened with His Dark Materials), although the fandom now prefers that if there is another attempt at an adaptation it has to be a TV series and animated.