I've argued before why this is one of the most underrated books by HP fans. No one seems to love this book. I just finished rereading it and I have two hypotheses. I feel like it could possibly have something to do with how Rowling re-explains concepts introduced in Philosopher's Stone. It's like those 4 pages that are in every Baby Sitters Club book: they explain how the club was formed, who's in the club, and what they do. I used to be able to recite those pages. They served the purpose of familiarizing readers who didn't start with book one, because it wasn't a plot heavy series. You find it in practically every long running series out there. It makes sense.
But with Harry Potter, there's really no way you can just pick up a random book and start reading, so there's no reason to have all of this extra explication. Even if you've seen the movies and think you'll be able to understand, you won't. Your first question will be, "who the hell is Peeves?" It's like trying to understand an episode of LOST if you've never seen it before. The only difference is that a LOST fan will punch you in the face if you try to ask a question while it's playing. True story, we punch.
Anyway, after I finished rereading, I realized just how much the cover art gives away. The cover is practically the entirety of the last 3 chapters of the book! What's there: Fawkes, the sword of Gryffindor, snakes galore, the basilisk's eye, Harry, Ron, and Ginny. Then there's Mrs. Norris, which makes no sense whatsoever, but oh well.
Going into the book, there's really no question about what's going to happen. The other books all have cover art related to their endings as well, but they're a little more cleverly disguised, with the exception of Harry and Hermione riding Buckbeak on the cover for Prisoner of Azkaban. So was it because we unconsciously already knew that nothing bad was going to happen in this book?
I can never convince anyone that Chamber of Secrets is better than it seems, but that's okay. One last thing though: Hermione saves the day whilst unconscious. What did Bella do when she was practically comatose in New Moon? Nothing. Trees were killed so that the months she did nothing could be marked by empty pieces of paper. Even if that's an unfair comparison, an unconscious Hermione accomplishes more than Bella on her most active day. Just sayin'.