I just finished reading this new installment of J.K. Rowling's masterful saga. Absolutely brilliant. In direct contrast to the juvenile coming of age tales that the first 4 books provided, this latest one (6th one and second-to-last in the series) is quite serious and ominous, though not without the standard dose of hilarity, paranoia, and enjoyment. I feel as though Rowling's writing is developing with her characters, becoming something more meaningful and heartfelt. The first few books felt like kid's books, even laughable at times in their attempts to portray a serious and totally involving story. This one changed my perceptions of Rowling and her series. Granted the fun still lies in the characters, the settings and the stories, in that order, but her tales have become more believable and more engaging as they begin to lead to some as-yet uninvisioned climax.
If you liked the previous book, this one is better.
If you have yet to delve into the Harry Potter Saga, I strongly recommend reading book 5 and then this one, book 6. The books are becoming distinctly more adult in their tone and stories. These are no longer the kid's books that the first ones are. (Do not take this to mean you should ignore books 1-4. Rather if you lack the patience to read them, books 5 & 6 make a good mid-way starting point.)
I can hardly wait for book 7. If the current trend is anything to go by, it will be the best one in the series.