The review below was based on my first read of the Harry Potter books, ages ago and in Dutch. Updated reviews will follow after a reread (in English) I plan to do.
When I first read the Harry Potter series, almost ten years ago now, I was mostly looking for what made people think it was a great series. I never read a lot of fantasy as a child, and was only slowly starting to appreciate the genre.
I think this is what I was still a bit feeling when I read Harry Potter and the Chamber of Secrets. I remember it as quite nice but also still quite slow and quite childish. It's already listed for reread (and very few books are) because I would like to get a better view of the book, also more in perspective. Hope to do it somewhere in 2017!
But what I've always liked best about the Harry Potter universe is everything surrounding it. That a whole generation grew up with it and will get your references, some of things fans have created around it. I think that is great.