Straight away I'm going to say I didn't quite like The Chamber of Secrets as much as The Philosopher's Stone. It's arguably too thin, with some irritating characters, and not as much of the first book's magical feel. But I still raced through it, taking just a slight bit longer due to the book's additional 30 pages.
So why didn't I like this as much? Well... it's quite easy to sum most of my issues up with two words - the characters. Lockheart, Creevey, Dobby... What a "joy" it was to read them. Lockheart was creepy and overbearing for essentially all but the last few chapters, and you just wanted to scream at him to leave Harry alone and to stop lying. Creevey is much the same, except he doesn't lie. He just follows. And Dobby is a very strange Chekov's Gun, but it's great fun to watch him fire... it's just a shame you have to put up with his cryptic and irritating appearances. Malfoy's arrogance seemed to be turned up a notch, which didn't do anything but add to the sometimes-annoying dialogue.
I also think my other major problem was the way the plot was handled. Rather than being a logical progression, it was Major Reveal, Small Plot Advancement, Major Reveal, Small Plot Advancement, Major Reveal, Small Plot Advancement. An example would be the whole polyjuice aspect of the story - a lot of time is spent building up to it, but the payoff is almost pointless, because the one important thing they learn doesn't really have much of an impact except to knock down one more tile on the Guess Who? board of the plot, and it's one you suspected would go down anyway. The advancement of the plot seems very quick, too, but I think that's mostly because this book shares the first's inability to really convey any long passage of time, because it hops from one moment to the next, leaving out months at a time. I doubt this will be as much of an issue with the later books, especially once I get to book four.
That all said and done, it's still a really good read. I don't think there was anything in it that I felt stood out to me, but it was just as compelling and just as fun to read as the first. The mystery was well-handled for the most part, and whilst at times it seemed like we were going the long way around to get some of the clues - indeed at times it felt like a series of set-pieces strung together with vague links - you were still gripped because you had to know who it was and why.
Summary: A book that's easy to criticise with what feels like no real stand-out moments. But it's just as engaging and as gripping as the first one was, and is hopefully just a blip as the series changes gears. This won't be my favourite Harry Potter book, but it was still a good read.
Favourite Moment: Ron and the back-firing slug spell. Excellent use of the squick factor there.
Least Favourite Moment: Basically every second we had to put up with Gilderoy Lockheart.
Improvements From Earlier Book(s): The number of female characters does increase, and there's a little bit more agency for one or two. So that's good. I'd also hope that the progression of time is smoother and a little more natural in the later books.