Now, I suppose this will be a little bit longer than the review I posted a few days ago, but honestly, I don't have a whole lot I want to say about Harry Potter and the Half-Blood Prince. Of course, I really do have a lot to say about it, but I think I'll save most of my thoughts for the post-mortem on the whole series.
I am pleased to report that The Half-Blood Prince is, as Brent would agree, easily the second best of the first six after The Goblet of Fire. Somewhere between the third and fourth book Rowling took a writing class or something, and since then the books have taken such an uptick in quality that I would call the last three particularly above my expectations (while the first two and maybe three decidedly below them). Furthermore, HP6 lacks many of the structural and pacing qualities that made Order of the Phoenix so unpopular. If there is anything to be said against HP6 that doesn't go for the series as a whole, it's that until the very end there it lacks a sense of direction and eventfulness that the other books have in spades. In both HP4 and HP5 there is the sense of inexorable forward progress, that the events of each book are leading toward a showdown at book's end--The Triwizard Tournament finals in the former, the mystery of the prophecy and Harry's worsening dreams in the latter. In HP6, there is ultimately an important scuffle between the Death Eaters and the Order, but it sort of comes out of nowhere. It's almost as if HP6 is a stop-gap book, between the fifth and seventh books which are more important plotwise (disregarding that one big thing at the end which I will not discuss).
Celebrity is a big theme in the Harry Potter books, and the fifth and sixth books form an interesting dual commentary--in the fifth, Harry is an outcast, ridiculed by the Ministry of Magic and reviled by his classmates; in the sixth his popularity has reached a fever pitch. The new teacher this year is Horace Slughorn, a Slytherin who wants to "collect" Harry as a member of the "Slug Club," comprised of all the best and brightest at Hogwarts. This is clever for several reasons, I think--for one, Slughorn is the first Slytherin who likes Harry and isn't evil; it's a great opportunity for Rowling to show that Slytherin doesn't completely produce Death Eater types and retain Slytherin's reputation for elitism and entitlement. Meanwhile, the vicissitude of Harry's popularity--persona non grata one day, schoolwide stud the next--is a sharp commentary on the nature of fame in the Muggle world.
Anyhow, I think I'll save most of my other thoughts for book seven.