I've read the books. I wasn't a very big fan of them because I had heard everything about them and went into the books with high expectations. They were okay, but I didn't think the hype surrounding Twilight was deserved. I didn't have high hopes for the movies.
The movie, though, exceeded my expectations. I thought it was better than the book because they had trimmed out the unnecessary fluff and whining that Bella was so prone to.
If you go in with an open mind and realize that you aren't going in there to see the book on screen but rather a film, you'll enjoy it. The cinematography is edgy, the script is fantastic and very funny, and despite reviews, Kristen and Robert have a ton of innocent chemistry.