The last Harry Potter book, Harry Potter and the Deathly Hallows, is by far my favorite of the seven. I finished Book 6 — which I did end up liking much better than I had the first time, by the way — late Saturday night, and immediately started reading Book 7. By the same time Sunday night, I had finished Deathly Hallows — I just couldn't put it down! I figure I read the entire thing — all seven-hundred-some pages — in about nine hours, tops.
There are a lot of things I could say about Book 7...but knowing that a lot of people probably still haven't read it, I don't want to give too much away. Suffice it to say that it was a perfect ending for the series. J.K. Rowling tied up all the loose ends quite nicely. I especially like Snape's role in the book...though what that is, I won't tell you.
It's hard to put into words how I feel now that Harry Potter has ended. However, this cartoon by Debbie Ridpath Ohi says it better than words ever could.