After J. K. Rowling's first two fun and magical boarding-school adventures, Harry Potter and the Prisoner of Azkaban seems to be the point at which the series starts to assert itself as something extraordinary. The first two books worked well as connected, stand-alone stories, setting the scene for Hogwarts and the wizarding world. Although there is still much to learn and discover all the way through the series, book three is where, for me, The Story really begins.
Prisoner of Azkaban has a noticeably darker tone than its two predecessors. I will state this once, and in my reviews for the rest of the series you can just take this for granted. Each book is darker than the last. (When the last few films have been released, this information was announced by reviewers as if it were some great surprise. We all know it. Let's move on.) So far, despite events at Hogwarts, the wizarding world as a whole has been at peace. Now, there is a flutter of fear in the air. Notorious mass-murderer Sirius Black has escaped from the supposedly inescapeable Azkaban Prison - and all the evidence suggests that he's trying to kill Harry. The Dementors, shadowy prison guards who spread despair wherever they go, have been set to guard Hogwarts, but they don't seem to be doing any good, and their presence is having a serious effect on Harry. Thankfully, for the first time there is a competent Defence Against the Dark Arts teacher at Hogwarts: the mild-mannered Professor Remus Lupin, who gives Harry some valuable extra coaching. But Lupin has some dark secrets of his own...
Prisoner of Azkaban is one of my favourite books in the Harry Potter series. There is less world-building and more plot, a twisty, page-turning and very satisfying plot. We learn some of Harry's family history, about Harry's father at school, and about the circumstances leading up to their deaths. Harry starts studying two new subjects: Divination and Care of Magical Creatures. Although both of these classes are crucial to the plot of this story, it is probably Lupin's extra-curricular Patronus charm lessons that are the most valuable to Harry. In later books, the Patronus seems to come as second nature to Harry, passing it on to his fellow students, and I forget how advanced magic it is, but for Harry, aged only thirteen, to produce a Patronus is extraordinary.
Remus Lupin is one of my favourite characters in the books - and the first sympathetic werewolf I ever encountered. Rowling managed to change the way I viewed some of the typical "monsters" of fantasy and horror writing, and influenced a couple of werewolves into my own writing. Again, I was blown away by the twists and revelations that came at the end of the book, and by this point it is apparent that the books are coming together to lead up to some bigger event; that the stand-alone stories are just chapters in a seven-volume epic.
