I finished Harry Potter and the Prisoner of Azkaban today. Though I didn't really enjoy the first two all that much, especially as they fuzzed together instantly, I liked this one. I think it helped that this time I saw the movie first and enjoyed it rather more than the first two movies, so I had some expectation that I'd like the book going in.
Without going into detail, I found this one more engaging in terms of both the story within the book and the advancing of the overall arc of the series.
So I'm now halfway up the ladder of completed HP books (in book count, if not page count). I am, at least, now looking forward to reading more.