By day, I'm a domestic violence prosecutor. By night, I read romance to restore my faith in love, relationships, and humanity in general.
Unlike earlier books in the series, which I've re-read many times (I used to re-read them while waiting for the later books to come out), this was the first time I'd revisited Harry Potter and the Half-Blood Prince since I finished the series. It's a very different experience, reading this book now that I know how the whole epic conflict with Voldemort works out, than my relatively-unspoiled first reading. (At the time, there were rumors that a major character died; I had my theories but scrupulously avoided any media where spoilers might lurk, and I read the whole book in two days on the day of release, so I got to enjoy, er, experience the surprise.)
This second time through, knowing what's coming, it strikes me that Book Six is actually very bittersweet. Half-Blood Prince isn't as dark and brooding as the preceding book, Order of the Phoenix. Now that Dolores Umbridge is gone, Hogwarts is a bright, happy place again. Now that the O.W.Ls (standardized testing for wizard students) are behind them, Harry and his friends seem to enjoy their classes more; they are less pressured, more leisurely. They find time for romance, for quidditch, for weekends in Hogsmeade, for learning how to apparate. Harry, who was furious at being ignored by Dumbledore in Order of the Phoenix, is back on good terms with the headmaster again: he's even singled out for special one-on-one lessons aimed to help him defeat Voldemort when the time comes.
Book Six is the calm before the storm.
Outside of Hogwarts, terrible things are happening now that Voldemort is back -- the Daily Prophet is always full of stories of kidnappings, murders, and other tragedies that show the Dark Lord is gaining ground -- and Harry and the others are aware of these miseries but insulated from them. In these dark times more than every before, Hogwarts is a haven, a refuge, a bubble. Dumbledore is the only wizard Voldemort fears, and so Dumbledore's school is the safest place to be.(show spoiler)
Of course that idyllic calm can't last, and the conclusion is meant to set up the final book, Deathly Hallows. While it's not a cliffhanger in the traditional sense, the end of Half-Blood Prince leaves a lot more open questions than the relatively self-contained plots of the other books in the series. Again, knowing what is coming changed my perspective on the ending. The first time I read it, I was stunned and horrified,(show spoiler)
but this time, I approached the final chapters with a strong sense of inevitability.
Random Spoilery Thought:(show spoiler)
P.S. I'm going to use this for Sock Poppet's A to Z 2014 Reading Challenge to cover T is for Time (the book travels through time, moves through time quickly, or flashes back). I don't generally like Time Travel books and I might have time collecting this letter otherwise, but I think the memories that Harry and Dumbledore revisit in the Pensieve count.