I loved the books right up until Harry Potter and the Order of the Phoenix. Goblet of Fire was my favorite, but with Order things started to get too dark and depressing and it continued this way through Deathly Hallows. The story went from a boy who was trying to learn and become powerful enough to beat Voldemort to a angry man that began to lose everyone around him.
His parents, godfather, mentor and even friends had to be sacrificed in his battle against Voldemort. Many would say that Rowling simply brought some reality into the mix, but Deathly Hallows was chock full of depression and anger.
Deathly Hallows isn't a book that I would want my children to read. It's something that I wouldn't want them reading until they are older and can process and handle the events that go on. As a story, I found Deathly Hallows rather boring in comparison to the other books and the flash forward ending left me unsatisfied
As a writer, I know the difficulty of an epic ending, but Harry Potter ended with a whimper and I had a difficult time getting through the book. I put it down several times only to pick it up again a few weeks later. I ended up reading books in between and when it was finally over I was simply relieved to be done reading it.