As a vampire fan from way back, and after hearing my 13 yo son talk about how the girls in his class were all about the movie, I was intrigued with the Twilight series and bought the first book to read before I saw the movie. It's an easy read -- not like the Harry Potter series where you have to learn a whole new vocab. To me, it also read like a classic romance, i.e., Romeo and Juliet, Jane Eyre, where things like age aren't taken into consideration as much as they are today as much as maturity of the characters.
I saw the movie over the Christmas holiday when my sister was visiting from Miami. Her dh and my son declined the privelege and sought another movie in the cineplex. We both loved it. I agree with one other reviewer that Bella was a little too naked in her bedroom. The book always describes her as in her sweats or in pajamas that I always took to me she was decently covered. I also agree with the reviewer who said in the movie the kissing was more intense than in the book. Edward is much more controlled and a gentleman in the books.
This first movie is more than appropriate for 13 year olds. I don't think I'd take a child younger than that only because girls these days get so much boy/girl stuff thrown at them as it is. That being said, I have also read the rest of the series and while Stephanie Meyers does an admirable job of keeping the romance and sexual tension at a young adult level ***SPOILER ALERT*** until Bella and Edward get married, once they are, there are several, while not explicitly graphic sexual scenes, ones that as a parent I don't necessarily think are appropriate for 13-14 yo's. So I don't know if I would let my daughters read all the books until they were older. Maybe. They are only 5 and 6 right now. I don't know what their maturity level is going to be when they get there. I am very curious to see how all the books play out as screenplays. That is why the title of my review is that parents need to know their kids for both the big screen versions and the books -- as well as see and read them for themselves.