When I first read this book, I wasn't quite as fond of it as I had been of the first. The new teacher was painful, and the darkness seemed too dark. Still, the magic was still there, and over the years, it has grown on me. Not the least because of a certain blond in the movie version.
For me, this second story boils down to two points - the Malfoy family, and Tom Riddle.
I'm a great fan of the Malfoy family, and the details we get about how the family works in this story are quite lovely. Not only the father/son relationship between Lucius and Draco, but also their place in the world, and far more details about their beliefs.
And then there is Tom Riddle. I won't go into too much detail here to avoid spoiling others, but I'm very fond of Rowling's flashbacks in this series, and this book is the beginning of those. The history of Tom, and of the Chamber, lend so much to the later books that there is no way to unwind it all until you have read the very last of the books.
One of my major quibbles with Rowling's work is that she seems inclined to write off her dark characters as irredeemable, no matter what their crime. Whether they be Slytherin or from a dark family. This is the beginning of that. There were moments in this book where she might have planted the seeds of any of these characters' salvations, but she did not.
Still, even with that flaw, this early part of the story is fascinating. I quite recommend it.