Asklemmy

A Wrinkle In Time was fucking insulting.

I think it was much worse for people that actually liked the book.

The Black Cauldron

Well. It's clearly not a book, but Disney's Hercules was the first time I really felt disappointed about going to the cinema. My ten year old brain was having none of it. I wanted the adultery, the murder, the dirty stuff the story was supposed to have and I think it's the Disney film (that I've watched) I hate the most up to date.

The NeverEnding Story

If TV shows count: Earthsea.

It was such a poor adaptation that Ursula Le Guin wrote an article denouncing it.

The witcher is pretty bad.

Queen of the Damned was pretty awful and threw out the majority of the storyline.

Hunger games.

Inkheart by Cornelia Funke is one of my most beloved series

read that series several times and when they announced a movie I was so hyped!

and the movie was just ok :C
I haven't seen a movie based on a book since then unless it receives high praises which I haven't seen much

Not a book and not a movie, but that Cabinet of Curiosities series adapted a couple of HP Lovecraft stories and it was fucking terrible. There were a couple of beats that were interesting, but generally it was very faithless and the changes were for the worse. There were some excellent episodes otherwise, but I can't help but feel that they are just butcherings of much better stories that I haven't read.

Politically, it's way less bad than you'd expect, I'd recommend watching it. One of the best episodes had -- to someone as brainrotted as me -- an incredible hybridization of classic horror and battle anime logic. That one was probably my favorite one, though there was one where the protagonist looks just like the Disco Elysium guy and kind of acts like him too, and it was fun.

P.S. did you know that there are movie adaptations of Ayn Rand's drivel? If you are masochistic, they might be fun to watch

The vampiers assistent, bases on the Darren Shan series. The tried to fit the first 3 books and the last one in one movie, and skipping over the other 8 books.... And who is Rebecca the monkey girl.... I wand Debbie and Sam....

Don't know if it counts as "classic", but Mortal Engines comes to mind. The film cut out over half the book. I loved the book and got really excited for the film, but it was a massive let-down. They could've easily made the film twice as long, maybe more.

Taras bulba. the american version focuses way too much on the love story. The sets are awfull. Taras does not even get burned at the stake.

The russian verssion is better. But it still misses the point. It plays it straigth while the book is suposed to be satire. They kill his wife at the begining using it as a justification for the war, when she should die at the end as a consequence of taras being an ass.

The point of the book is to show that the myths of the russian frontiersman are bullshit, because if they really acted like taras does they would all get whiped out.

Gogol is still an arch reactionary and you can tell he geuinley beleves some of the things he is moking. So its suposed to have a silly ironic self mocking sligthly nhilist tone. Remininicent of a lot of stuff in the internet. But both adaptations play it straigth and pay too much atention to the polish girl.