Going to see a movie for a book, it was in my expectation that it would of course not follow along EXACTLY. But after seeing 'Twilight', I found it didn't bother me. Though the movie may not follow along with the book in it's entirety (which there are very few, very minor things which they dont), the differences were minor and seemed unimportant in contrast to how wonderful the movie was.
In my opinion, each character was wonderfully portrayed and the story was served justice. It was very funny and highly enjoyable to watch. Though there were many things a person would not understand had they not read the book.
If you are a Twilight fan, or even the slightest bit interested, the movie is definitely worth watching.