Anyway, if you know the book or the characters then you'll be pleased to know it is better than the first movie. It is decidedly darker and has many more CHARACTERS to enjoy, particularly Jason Issacs' Lucius Malfoy (with his Viggo "Ghostbusters II" hairdo) and Kenneth Branaugh's Gilderoy Lockhart. If you don't then you might very well enjoy it anyway but you will probably be as lost as a mud-blood.
It is all a bit of a trifle anyway. It really does mean nothing, but you will be plenty entertained for three hours, making this a ILM Value For Your Entertainment Dollar selection.