Man, was that a ride.
It's tough to write this review without giving spoilers to the six people out there who have yet to read this but are planning to do so. However, I'll do my best.
This final book in the Harry Potter series is the most dramatic and the most bloody. It's basically about the final showdown between Harry and Voldemort, with all the other characters taking up arms on one side or the other. Rowling has done a great job of tying together a lot of small points from the previous books which make the revelations in this one feel genuine. None of that "And poof, he was a hamster the whole time!" bull. Nearly everything that happens has its origins in the other books of the series. Plus, the "Battle of Hogwarts" ranks right up there with the battle of Helm's Deep as far as fantasy battles go, IMO.
This book is also a LOT darker than I was expecting. There is a lot of death in this one, and it gets pretty emotional. Yes, I might have been that near-thirty-year-old you saw riding through Boston on the T during rush hour, bawling her eyes out. I didn't even realize how attached I was to these characters, but considering this book in itself is massive, and combined with the other six books I've been with them for THOUSANDS of pages, I guess it makes sense. Anyway, although this is technically a children's book, this is NOT for children. I think this is definitely PG-13.
The only thing I disliked (and I find I disliked it strongly) was the epilogue. It seemed to be slapping a neat bow on to the end of a book that had been dark, twisted, and wrenching. It almost felt like the ending of a fan-fiction--nineteen years in the future, the surviving characters gather with their numerous Children With Significant Names to talk about how wonderfully life turned out and how lucky they all are to be alive. Although I was interested in the lives the characters went on to lead, I found the last chapter frankly a little insulting. It was the only real low point to an otherwise gripping book.
Clearly I wouldn't recommend this to anyone who hasn't read the series. However, for anyone who might have gotten bored at book five and given up, I highly recommend you get books six and seven--they are totally worth it.