I'm not going to go into a complete book review here, since if you're really into HP you've probably already read the book. On the other hand, if you don't care about the series anything I have to say would fall on deaf ears anyway. I just had a few brief comments, having finished the latest in the series just yesterday.
As usual, once I get started on one of Rawling's books I can't put it down. These WAR & PEACE size books are not the easiest subway reading, but the hour plus commute I make back and forth each day certainly gives me time to spend at Hogwarts with Harry & Co. The war between the Death Eaters of Lord Voldemort (or "He Who Shall Not Be Named") and those allied against him is beginning to get bloody enough to have come to the attention of Muggles (we non-magical folks). After the events of the previous book, Harry is even more determined to find and destroy the Dark Lord, who killed his parents leaving Harry scarred and in the not to kind hands of his mother's relatives.
Each of Rawling's books covers another year of Harry's time at Hogwarts, the school for wizards and witches. This is the sixth book, finding Harry, Ron & Hermione confronting not only the dark forces but also teen age problems we all face. There's quite a bit of snogging going on here, so be forewarned.
(Aside: When the term snogging first appeared I couldn't help but recall the Monty Python sketch dealing with the worst family in Britain and the father's arguing with her daughter about her 'snuggling' with her boyfriends. )
SPOILER ALERT: Sadly, one of the more popular characters doesn't survive the events of the book and we can only see how this will in turn effect what happens in the next & final book in the series. END SPOILER