This game follows the plot of 'Harry Potter and the Chamber of Secrets', so if you've read the book and/or seen the film, you'll find it all quite straightforward - and it's not very difficult anyway.
As you progress through the game (and the story), you learn new spells and find hidden items like Bertie Botts beans and wizard cards. There are a number of little sub-games which have to be completed to progress through the story, but unfortunately these all tend to be of the same kind - mostly sneaking around corridors without getting caught by Prefects, Snape or Filch.
There's some Quidditch and broomstick flying involved, but the controls for this were rubbish and made these parts a bit of a chore to play.
The beginning of the game seems to be packed with subgames and things to interact with, but this really peters out and by halfway through the story, there's very little to do except watch the cut scenes to get to the end. Maybe the makers ran out of time, or just got bored with it. I think I finished it in about 4 hours - it's a nice looking/sounding game, but certainly no Zelda if you wants a few weeks of play out of it.