I am just failing to have any feelings about this whatsoever.
I mean, I was fairly tipsy for a good third of it, so that doesn't help.
In Prisoner of Azkaban, Harry discovers that a dangerous criminal, Sirius Black, is on the loose and wants to kill him.
That's pretty much it. That's what drives the book.
I think that's why I didn't enjoy it as much as the first two: while Chamber and Philosopher both have strong, tight plots, Azkaban, while it works in hindsight, just meanders along for a bit, relying on our interest in Hogwarts and magic rather than any inherent tension to keep us reading. Admittedly the Dementors are fairly scary, but Dementors alone can't drive 317 pages of plot.
(Incidentally, I was really annoyed by the fact that Rowling tried to create a mystery around the Dementors by having everyone refer to them as "the Azkaban guards". "Those Azkaban guards, they give me the creeps!" It begins to feel like a Blackadder joke after a while.)
So, yes. Not my favourite.