Though it does make some reductions/alterations to the story as compared to the book, the spirit and impetus of the source material has stayed intact, and a few small additions (Hedwig's moment) and the dancing scene between Harry and Hermione actually helped tell the story and connect with the characters, unlike many of the departures from the books in earlier movies which seemed largely pointless. The Tale of the Three Brothers was, as others have mentioned, handled in a very imaginative way and the performances of all the players (not just the kids) were all the strongest they have been so far. "Prisoner of Azkaban" was the last time that I thought a HP movie really captured the feeling of the book it was based on, but now that film has been at least equaled and probably surpassed. Yes, having read the book is probably beneficial to the viewer (if not absolutely necessary) but honestly...these are the most widely read works of popular fiction in human history, and a very easy read at that, so I don't have much patience with those who expressly refuse to read them and then complain that they can't follow the movies.