Only one exception that I can think of - Forrest Gump.
Not always. The movie “Jaws” was better than the book. For example, it cut out the extraneous crap like the fling between the sheriff’s wife and the ichthyologist, which added nothing to the story.
One of many, but one sticks out in my mind. One Flew Over The Cuckoos Nest pretty good movie; amazing book. Chief narrates the book but is something of a secondary character in the movie.
With the exception of “Jaws.” The book had a patently ridiculous ending and Spielberg improved it by leaps and bounds. The affair Hooper had with Chief Brody’s wife was.... Just stupid.
Jaws
What if the book sucked? Jaws, The Godfather, The Shining...
Not always. I know Disney’s The Little Mermaid is actually quite a bit better than the original tale, getting the intended theme of self-sacrifice down FAR better than the original tale did (not to mention made the lead character a lot more sympathetic if you ask me. Sorry, but 1. I find it extremely irritating that God would fail to give a species that wasn’t just sentient, but sapient as well, at the very least something similar to an immortal soul if not an immortal soul itself, and 2., I just found the mermaid in that story to be very unlikeable, especially when many of her actions have dire consequences for her family, she left for a very selfish reason regarding pursuing a soul, and unlike Ariel, she doesn’t even ATTEMPT to make amends for what her actions caused her family even when she committed suicide. And she gets a soul? Had it been me who wrote the book and in Andersen’s shoes, I’d probably have her cast down to Hell for what she did.). I guess I could also cite Jaws and Forrest Gump, even though they weren’t exactly my cup of tea either in book format or film format.
That all being said, we can definitely agree that the book version was MUCH better than the crappy film adaptation in the case of Starship Troopers. Heck, it wasn’t even intended to be an adaptation of Starship Troopers the novel, it was originally a completely unrelated film called Bug Hunt on Outpost Nine.