This is my second favorite book, after Deathly Hallows. To my way of thinking, it is a gateway to the darker books. The younger characters become stronger, more in control of themselves, and generally more dynamic. The first two books introduced the characters and Harry's fight for his life and freedom from the dark past he can't remember, as well as his fight for the wizarding world as a whole. POA gives us a break from Voldemort by showcasing Harry's parents and family, and his father's friends. It also foreshadows much of the next plotline in GOF and OOTP, with the Marauders taking a major role within those books. Each book is a harbinger of the next books to come, which makes Rowling such a fantastic author.