What I love about books is the fact that you make the movie in your mind. When I read Twilight, I absolutely fell in love with each character. It was written in a way that I could get so lost in the story, I would literally find myself holding my breath. Even if you've never read Twilight, you know basically what it is about -- vampires. But, don't let that put you off. I was picturing some kind of Buffy the Vampire Slayer type of story with people running around scared... TOTALLY not Twilight. In Twilight, Bella Swan takes you into the secret vampire world and makes you fall in love with Edward Cullen and his family.
The movie was good. What I didn't like was Bella's character. She was so skittish in an acting-too-hard kind of way. Also, Edward can read minds. I would've liked to have heard through his mind... actually, it would have been better if the movie would have gone more in depth with Alice and Jasper's special talents, too. Another major difference was the book talked a lot about the Cullens' "vegetarian" diet, meaning they only drink the blood of animals, not humans. It would have been neat to see Edward and Emmett hunt. Having said that, I do realize that the book was narrated by Bella, as was the movie. Bella did not get to see them hunt in the first book... I don't know.
Oh yeah! If you have seen the movie, did you notice Stephenie Meyer sitting at the bar in the diner? I saw her right away!
Both movie and book were great. If you haven't read/seen either, definitely read the book first!