I just finished off Harry Potter and the Deathly Hallows. I missed all of the excitement, and bought it rather quietly earlier today, in a Barnes & Noble. No lines, no fuss. And then proceeded to read it. My brain is now full.
I am glad that I had just finished reading (and watching) Sorcerer's Stone, and caught Order of the Phoenix at the theatre first. IMHO, the "important" books of the series are books 1, 4, 5, and 7. 1 & 7 are obvious. 2 & 3 are basically character intros - though they set up some things for the later books (7 in particular). 4 begins and 5 finishes off th transition from childrens' books to Young Adult. 6 is, in the end, (and no disrespect to a fine book in its own right) a set-up for book 7.
Anyway, on to the review. No outright spoilers - especially if you've been paying attention to what has gone before.
Harry Potter and the Deathly Hallows is, first and foremost, the seventh and last in the Harry Potter series. On the other hand, it is quite definitely what I would call a Young Adult novel; decidedly not a book for young children. While I can hope my children (if and when) will enjoy the series as much as I have, I wouldn't want them to read it much before, say, 15-16. Definitely PG-13. Probably not R (though it could be made into an R movie depending on the
depiction of certain scenes - mostly involving Cruciatus). Also, it's long. I've read shorter Tom Clancy novels (though as I re-read some of them a while back, I find I prefer Harry Potter to Jack Ryan, both as characters, and as books). Perhaps it could have been tightened up, but at the same time, I would have missed some of the "additional" scenes. I've read other people's reviews about the book, and one commentor did mention that there seemed to be a certain amount of "name-checking", bringing back bit players from other books just to show them one last time as the series ends. There's nothign wrong with that, to me, as long as it's kept to a minimum. And it also serves the purpose of pointing out something very important - in the end, while it is about Harry, it's also about everyone else. Harry doesn't stand alone; as we've seen throughout the series, that's one of the things that distinguishes him from Voldemort. There is a certain amount of deus ex machina (though the author is good enough to not spring them on the reader entirely unawares), and very little is left unexplained. That which is left unexplained, is left there because it has to be. Just as CS Lewis leaves the Deep Magic unexplaine din his own way, there is Deep Magic of Harry's world that is equally inexplicable. It is understandable, to a certain extent, by the very greatest wizards (who intuit it), but not explicable.
Two pieces of advice - on your first read through; don't look at the table of contents at all (terrible spoilers lie in wait) and don't read the last chapter first. It ruins rather a lot of the dramatic tension that makes some of the lengthier bits of the book so enjoyable, but at the same time doesn't tell you enough of the end to make it worthwhile. Skip the table of contents and read it straight through. The author has already said people will die - one fo the fun things about the book is that you don't know who it will be; and there are no obvious "exempt" characters. And by all means, enjoy the journey.