I just finished the book. It took a little longer to hook me than the others did. But the last 200 pages were pure gold.
Spoiler:
I'm pretty sure Dumbledore is dead. But have no fear, I am sure he will be back in the next book as Dumbledore the White.
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Spoiler:
I think Dumbledore had to die, for the same reason Obi-Wan had to die. Just as it wasn't Obi-wan's destiny to kill redeem Vader and kill the emporer; It isn't Dunbledore's destiny to kill Voldemort. Both of these men were great and powerful, but their power was waning. By striking down Dumbledore, Voldemort has made him more powerful that he can possible imagine. I see two possibilities. Either Dumbledore and Snape worked out a plan where Snape makes Dumbedore a martyr by killing him infront of Harry. Or Snape is truly evil and struck out at the man who has shown him such kindness. I think it will be the latter of these two possibilities. I like that idea better, because I think Dumbledore played Snape like the fool he was. He kept Snape around, because he knew Snape would kill him some day. He needed to die at the hands of Voldemort's lackies because he needed to give Harry the focus necessary to rise up and defeat Voldemort. His death will not be in vain. It will be the turning point of the war, and that is the way he wanted it.
On a different note, I didn't think I was going to like these books. But I guess I was wrong.