I actually watched the movie in a literature class in college. The reason for this is our literature professor also had a passion for film, and wanted us to watch the film as if it were the book/a piece of literature then discuss it/write about it as such. It was actually an interesting class format, we did the same with Se7en and Fight Club as well.

Anyway, with all that said, I really enjoyed the movie/story, and have always meant to read the book to see what differed. However, like a few others have noted, it seemed to drag on/fall apart a bit towards the end.