The boy brought home Harry Potter and the Goblet of Fire last week, and I must say it's a big improvement on the book. It's got all the main plot bits and none of the boring padding in-between. The stand-off with Voldmort, at the cemetary, was good and scary. The only gripe I have, and this extends to all the Harry Potter movies, is that Hermione is far too pretty. In the book it's a really big deal that she turns up to the ball with straight teeth, no glasses and tamed hair, thanks to a glamour. In the movie all she has to do is wear a slinky dress and put on some makeup.
The Lord of the Rings movies, in the boy's opinion, are also much better than the books. I'd be inclined to agree, except when I tried to read the books I was never able to find Fellowship of the Ring at the library. Starting this story with The Two Towers was every bit as confusing as you'd expect.
What are some other movies which turned out to be better than the books they were based on?