Quidditch makes a return after a brief hiatus in Order of the Phoenix, but it's less imaginative and even less fun than making potions. Furthermore, the game's plot takes liberties with the source material, putting Harry in preposterous positions that clash wildly with the book. Hermione's long hair hardly moves, Professor McGonagall is cast in perpetual shadow, and Ron is cursed with a laughably small head. The character models are based on the actors but are poor imitations of their real life counterparts. None of the movie's actors lend their voice talents, so you'll have to make do with sound-alikes who sound little like the real people. The cutscenes are not only short and sporadic, but they are also poorly acted and look awful. But you'll have to fit these pieces together yourself because the game doesn't spend any time filling in the details. There are a couple of references to the titular Half-Blood Prince whose notes dot Harry's potions book, a trip or two through Dumbledore's memory to see the young Tom Riddle, and a quick peek at Harry's ever-growing suspicion of Draco Malfoy. The story is barely comprehensible if you haven't read the book beforehand.
