I'll post this book to take place for the whole series. I love the HP books. I really see the first 5 books as a lead up to the 6th and 7th.

What strikes me most about the series is the growth of everything involved. Throughout the series, JKR's writing matures, the characters mature, the storyline matures, the themes mature, etc. It's impressive to follow the maturity of all aspects of the books. Thanks JKR.