I first watched this film before I had read the books, and although I enjoyed the romance element of it I didn't fully "get" it. I was told to read the books, which I did and was hooked from page one, I then re-watched the film and completely fell in love with it now that I understood the back story to it.
Is pretty true to the book, one of the truest adaptations I have seen, although 1 scene is not from the book, and I would have liked to see a particular classroom scene from the book instead of what they did in the film (should have been blood typing rather than recycling scene)
If you are going to buy Twilight on DVD and you have been swept up in the Twilight Saga phenominem I would wholeheartedly suggest the 2 disc version because there are hours of extras which are really interesting. If extras don't bother you maybe go for the cheaper 1 disc edition