Harry Potter books are like popcorn. You start with a page or two, and before you know it, you have read two books and 1500 pages. And you have no recollection at all as to what it all was about. It was exactly the same with Harry Potter 2&3, which I read some 5 years ago – within two days.
The girth of the Harry Potter books has since increased, the content has stayed the same. Two notable exceptions: Harry Potter is discovering the opposite sex – but this was deemed unimportant enough to warrant only a few furtive glances in HP4, and a single, prematurely terminated date in HP5. I guess that if more space had been devoted to this topic, it might have gotten in the way of some very important heroing or worldsaving or darklorddefeating. The second exception is that Ginny Weasly is maturing into a real character – she even speaks and has her own opinions! She is a valuable addition to the cast, and in difference to Harry, she doesn’t have any problems with the opposite sex: By the end of HP5, she already has her second boyfriend.