I’m slightly ashamed to admit the only book I’ve ever read made into a film was Layer Cake, I love them both.
They’re slightly different, the author also wrote the screenplay and gave his reasons for the changes, mostly screentime limits meant certain characters needed to be cut, scenes lost etc but the maintained the core of it.
Best of all he made an asset out of a liability – spoilers follow:
In the book, due to a terrible case of mistaken identity a tourist is murdered, an American one at that which would have been bad commercialy for the US backed film, they could have changed it a little, but instead he made it a massive plot twist, it’s good for the film viewer, but great if you’d read the book and expected it to go one way when it suddenly goes another. I really liked that.
Neither are a classic, but I like them.