I am a fan, not a fanatic, of the Harry Potter books. I have never read the books more than once. My favorite is still "Goblet of Fire". To a lesser degree, I am a fan, not a fanatic, of the film adaptations of the Harry Potter books. In this case, the best film (by far) of the series has been The Prisoner of Azkaban, a film I have seen many times. Although also a superior book, the film to date has been the only one I felt has captured the essence of the book and improved upon it.
This is not a requirement for a film adaptation. Rowling's books are sprawling works that (after Azkaban, the last "short" book), were typically over 700 pages. Film adaptations are hard enough with short material, but the Potter books also present a situation where material MUST be left out in order to keep the running time under 4 hours. And why must a film be under 4 hours, or 3? It doesn't have to, but the point is to entertain, not catalog events to screen. The film is an adaptation for a larger audience, not just those who demand to see every single scene transposed. I truly feel sorry for one of my Potter fanatic friends who couldn't wait to see her favorite line from the Half-Blood Prince shown on screen. It wasn't. And she felt that overall Harry Potter and the Half-Blood Prince was a let-down for that and continuity errors between it and the book.My policy on seeing a film that is an adaptation from a book is, if I have read the book, I need to allow a minimum of a few months before seeing the film. Never, ever read the material before you go into the theater (Potter fanatics do this, you see), for then you are ticking off your moments. I can't think of a better way for me to ruin my own fun. This all started back when I read High Fidelity, and then a week later went to see the acclaimed film adaptation. Despite the rave reviews, the film was such a faithful adaptation that I was UTTERLY BORED watching the film. I just ticked off the plot points as they happened. In short, reading the book totally ruined the film for me. But I love reading, and I love film, so I had to adapt a buffer strategy.
The stategy served me well with Azkaban -- I had forgotten so much of the end that I was actually surprised when it was revealed who was the stag in the forest, and of course I kind of teared up. Those moments are magical for me, but it would have been ruined had I just been waiting for it to happen.
Which is why I can say that I thought Half-Blood Prince was an entertaining film. No Azkaban, but what is? Now, I think it's brilliant to split the seventh book into two films to cover your adaptive bases (and make twice as much money!), and deserving for the series finale. Which I've read and won't be reading again before I see the films.