Number of pages: 766
The fifth book in the Harry Potter series is also the longest; unfortunately it is one of my lesser favourites, because it gets a little too talky at times, with J.K. Rowling throwing in a lot of exposition in some chapters (although she at least manages to tie up every loose thread by the end).
There was also a subplot involving Harry's romantic life that I was less interested with; sure, he's fifteen at the start of the book, so it was inevitable, but it mostly involves Cho Cheng, one of my least favourite characters on the series, who just seems like a distraction from the main plot.
I noticed that Harry seemed angrier than ever before in this book, possibly the angriest he gets in all seven of the books, and I found him annoying in places; he even loses it with Dumbledore a few times near the end, suggesting that he may be losing trust for him. In the penultimate chapter I wanted to give Harry a slap a few times and tell them that Dumbledore always knows what he is doing (this seems to be confirmed at the end of the series).
The main plot feels less like a self-contained story as the beginnings of a massive story arc that builds up to the final battle in the seventh book. Dolores Umbridge is a villain who seems inspired by Nurse Ratched from One Flew Over the Cuckoo's Nest (certainly I think that's who Imelda Staunton was channeling in the film), and it was good to see Mad Eye Moody and Lupin both returning, as well as a much bigger role for Sirius Black.
This is probably the first book where I started feeling sorry for Snape, in the series' second visit to the pensieve, where Harry discovers that his father (and Sirius) weren't especially nice when they were younger. James Potter seems more similar to Draco Malfoy in this scene, while Lily Potter seems exactly like Hermione. I also noticed re-reading this book that it confirms that, as I had suspected, Lily was also a mudblood, hence her sister Aunt Petunia not being a witch and her just being an embarrassment to the family.
The storyline does get more interesting as things go on, particularly in the final third; I enjoyed the climactic battle scenes, though not surprisingly, following the major character death (J.K. Rowling warned that someone would be killed off at the time of publication), the ending mostly feels very downbeat (aside from the codas on the Hogwarts Express and the station), only eclipsed by the ending of the sixth book.
I think I prefer the film over the book, since the director did a good job of abridging this down into one of the shortest films in the entire series.
Next book: Lethal White (Robert Galbraith)