The film adaptation of The Prisoner of Azkaban is better than the book.
The writing of the Harry Potter series becomes more sophisticated as the books progress. It starts with Philosopher’s and Chamber, which are written for a younger audience. The themes are relatively simple. Then in Azkaban, J.K. Rowling seems to decide that she wants to be more ambitious with the series. The introduction of Sirius Black, Peter Pettigrew, and Remus Lupin make the characters’ relationship adds a complexity to the mythology of Hogwarts that hadn’t been present in the previous two books. Further, it ends with very large plot threads unresolved. The narrative dividing line between books begins to be blurred, instead of most of the plot resolving at the end of each book. Finally, the series starts to take a more thematically complex turn, pushing the boundaries of “Young Adult” literature by Phoenix.
These developments, of course, are all good things. Much of the foundation of what makes Harry Potter so resonant and enduring to adult audiences instead of being a frivolous children’s book is laid in Azkaban.
However, the main problem that Azkaban faces as a book is that it relies on a narrative strategy used by the previous two. In Philosopher’s and Chamber, both of the big plot reveals and subsequent exposition are done in one scene: Quirrel is a host to Voldemort, and Tom Riddle’s diary was created by Voldemort. Both of these are handled very simply, and only take a few pages to explain. “Snape/Malfoy is just a red herring” is something that can be spelled out rather expediently. Other key moments of exposition are spaced sporadically through the final chapters of each of those books, but the core revelations of what has been driving the plot are delivered directly by the antagonist to Harry.
Where the Azkaban book goes awry is that Rowling attempts to have a similar scene of exposition where most of the plot elements are revealed in one fell swoop. The problem is that Azkaban is a much more complicated book, and attempts to give a much more ambitious rationalization for what has transpired. Rowling still resolves the plot with her trusty red herring, and it’s still satisfactory. However, the plot relies upon the complicated interactions of Peter, Remus, Sirius, and yes, even the rivalry between James and Snape. That’s a lot of information to get across for a simple, “No, Peter killed your father.”
Rowling tries to pack all of that information into one encounter between characters in the Shrieking Shack. In that one scene, which spans two lengthy chapters, takes an hour to read aloud, and takes place in real time, Harry goes from seriously considering murdering Sirius to accepting him has his godfather and wanting to live with him. It must also be noted that Harry’s internal monologue is not particularly revelatory either. There are many white hot flashes of anger, and little else.
Critically, she does not attempt a “one and done” expository scene in the future books.
I’m not opposed to long blocks of exposition in books. I often prefer the world and character building in novels to overt action. The problem with the Azkaban book is that neither the reader nor the characters is given no time to breathe and process one weighty emotional revelation after another.
How Rowling and long time Potter screenwriter Steve Kloves solve this problem is to expand this sequence, and break up the revelations into much more manageable chunks. Yes, the Shrieking Shack scene remains the emotional cornerstone of the film. But entirely added is the sequence where Harry sees Peter Pettigrew on the Marauder’s Map, and tells a visibly shocked Remus. And Sirius’s offer to have Harry come and live with him comes several scenes afterwards. These changes make the emotions at the end of the film much less jarring, and much more natural.
The relationship between the books and the films are complicated in that they gave Rowling an opportunity to revisit and rework her own material. Yes, certain things were changed simply because there was not time to include them in a two and half hour film. But I think it’s a mistake to consider the shift in medium to be the only reason for changes in the story. Other aspects of the adaptations can be read as conscious efforts on the part of the original author to improve her own work.