Asklemmy

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

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.

Eragon. They really fucked up so much about the book!

The NeverEnding Story

Hunger games.

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.

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....

Cloudy with a Chance of Meatballs should have never been made into a movie.

I know its not a classic, but Dan Brown's inferno the book and the movie have two different endings and it angers me every time.