I watched the movie long before I read the book. There are differences in the movie adaptation, but overall it's quite true to the book. I must say that reading the book made me appreciate the movie even more. I already liked it a lot and now I realize that the casting was perfect. I saw the actors while reading the book and it fit perfectly. I think I'll even go as far as saying that I liked the movie better. Some things could've been more fleshed out in the movie and it did some silly things regarding technology, but it's a very good movie, based on a good book.