Jay wrote:The Tri-wizard tournament in Book 4 was great..but Book 3 really introduced some of the cool aspects of the Harry Potter series. The dementors, Sirius, Lupin, and just the overall introduction of darkness into the series.
I agree, Jay.
Though, as I mentioned in another thread, when I go back and read book 3 (which I still think is my favorite--I think it beat out book 5 in the end just slightly!), I'll read it with some sadness because I'll know that Sirius is going to die and that Harry will never get to live with his Godfather.
Maybe that doesn't make anyone else sad, but it sure does make me sad!
I also really like Lupin, and reading that book and how he interacts with Sirius, one of his best friends and a reminder of the 'Marauders' will be bittersweet.
One of the things I loved best about book 3 from all the other books is that it broke the formula. Books 1 and 2, especially, were rather formulaic...which is why I suspect a lot of people didn't like book 2...it was ok in book 1, but then book 2 repeated the same kind of formula. Book 3 was a total departure, and though books 4 and 5 were darker, more detailed, and much more compelling than books 1 and 2, they still had the same basic formula: Harry faces down Voldemort at the end of the school year just in time to go home for the summer to the Dursleys. Book 3 was written to the formula at all. There was no show-down with Voldemort. The big confrontation, though exciting, wasn't the only climax in the book...then you had the time-travel (which some people didn't like, understandably). It was just a totally different book. There was lots of suspense and mystery (some of which you saw again in book 5 [and even in book 4, to some degree], which is part of why I liked it).
That's my take on why book 3 is my favorite as well as perhaps why it is other people's favorite book. Also (and again, you got some of this in book 5), you got to learn about all sorts of cool things like Jay mentioned: Dementors, the Marauder's Map, you went to Hogsmeade for the first time, you learned about Harry's parents and their friends for the first time, Lupin was the DADA and he knew James and Sirius so well, etc. Lupin is one of my favorite characters because I think (when Harry isn't being hot-headed and/or rude, as he was, quite a bit, in book 5), he's much more like the open-minded and modest Lupin than his father or Sirius. Harry, for *most* of the series has been rather open-minded in his choice of friends and rather low-key about himself. He isn't attention-seeking like the papers claimed, nor is he elitist.
Hagrid (a half-giant), Ron (a 'never-been-in-the-spotlight' kid from a poor family), Hermione (a know-it-all 'mudblood'), and Neville (a, until book 5
, klutz who can't seem to get anything right) are all people Harry values because he sees past the surface of them. Perhaps what we saw of James and Sirius in Snape's memory wasn't entirely accurate, but the response to "What's he done to you?" being "Well, it's more that he exists" (or something like that) doesn't seem to fit with Harry (until perhaps the 5th book when he got a chip on his shoulder and let off on people). Lupin and Harry had an interesting bond because Lupin really cares about Harry and taught him ways to deal with his fears and his emotions. I wish we had seen more of Lupin in book 5.
Now, I really want to go re-read book 3, to me, the best book in the series!
~ Lizzy
Certainly, it was a great book and I raced through it (again, because it was new? not sure). I'm not sure which is my favorite! I used to say Book 3 was, and then, when I read Book 5, it was my favorite, but Book 4 is great, too, in many ways. So hard to choose! Perhaps reading your posts I'll better be able to choose! 
