During the summer holiday at his aunt and uncle's house. Harry Potter (Daniel Radcliffe) is met by Dobby the House-Elf (Toby Jones) who warns Harry to not continue at Hogwarts as he will be n terrible danger. Dobby stops Harry's every attempt to get here but, with the help of his friend Ron Weasley (Rupert Grint), manages to get there in time for the year to start. In his second year, Harry finds a diary written by an ex-student named Tom Riddle and Harry begins to hear voice in his head. The school is also distraught when a message written in blood is written: "The Chamber Of Secrets Has Been Opened. Enemies Of The Heir, Beware"
So is this worse or better than the first? It's about the same. The Harry Potter franchise was still blossoming by this point so there wasn't anything that they screwed up yet nor is there anything that is really ground breaking and awe-inspiring...except the casting of Kenneth Branagh. Everything that was great in the first one is still present and is clearly a sequel (other than the whole 'same franchise' thing). The new cast such as the previously mentioned Kenneth Branagh and Jason Issacs, giving one of his best performances, are great but this is the film that contains a lot of one time characters which is a shame (well, except the odd cameo).
Magic is a big part of the Harry Potter franchise so naturally you'd expect it in every iteration...yup. Magic is just as good as it was in the first film which now features flying cars and trees bent on killing everything in site. There are also new mythical creatures for the series such as a giant spider voiced by a Bond villain (shudder) and house-elves. These things make the film's world come to life and the great effects used make them that much more real (I don't think Aragog was CGI).
Lots of people I talk to say that this is the best Harry Potter film and, you know what, I can see why. I wouldn't say that it's the BEST one but it is certainly in the better half of the Potter franchise. The acting is still great and the new actors further improve on this, the new magic elements are great to see and it's nice to get some backstory behind Hogwarts and some of its staff and students. Now if you excuse me, I have some pizza waiting (that's related because...I don't know).
A great continuation of the first film and is just as good...but not better or worse (okay, a LITTLE, TINY bit better).