Silence of the Lambs the film stayed relatively faithful to the book. The main difference was that there was no romance between Starling and Crawford in the movie. Hope that helps. In fact, I hope no such thing.
"Catch 22" was interesting. That was a book they said could not be made into a movie. It has to be said they made a pretty good job of it.
I'd like to watch Catch 22 but I think watching it might spoil the book. Similarly, I'd like to read the book but I fear the film would be a let-down afterwards. It's a problem that doesn't seem to have any solution.