As with Quidditch World Cup, I really like this game. However, I am a huge Harry Potter fan.
This is an unexceptional actionish/RPGish sort of game which is similar in control style (and pretty much only in control style) to Legend of Zelda: Windwaker. The player must guide Harry, Ron and Hermione through a series of puzzles and battles, closely related to and punctuated by plot points from the book by the same name. While characters and events from the book will be immediately recognizable by Potter fans, anyone unfamiliar with the books will probably not feel drawn in by the storyline, and will likely grow bored quickly.
Harry Potter fans, on the other hand, will love this game. Playing through some of the major plot points is very fun for HP fans, and the characterization (especially of the Weasley twins) will surely have HP nerds giggling.
So, all in all, graphics are decent, controls are ok etc. etc.... This game is unexceptional, but is a must-have for any true HP fan.