There are a few cases where I’d say the film was far better but also had little to do with the book.

Heart of Darkness/Apocalypse Now: Whole setting change and the movie production was an absolute shit show, but I’d say the final product outdoes the book by a lot.

Who Framed Rodger Rabbit: Literally has nothing to do with the book, turned a weird book into a revolutionary film for animation.

As for one where they are more comparable,

Fear and Loathing in Las Vegas: I love them both, and I know Thompson didn’t care for the movie. But at the end of the day I think the film successful captured the district voice and tone the book has, and handled the ending a bit better than some of the more weird disjointed stuff at the end of the book.