Great game. Very long, but story is decent enough to keep you going. My only real gripe is that its glitchy. Sometimes you'll get stuck and the only way out is to restart from last save. Luckily it autosaves very well so no real gameplay is lost. It's sometimes difficult to tell if the game is stuck in a glitch or if I've missed something, which can waste a ton of time. The playfield is massive, and there are tons of side quests to keep anyone sidetracked from the main gameplay, but in a good fun way.
Even with the glitches I'd recommend this game to anyone that likes story & free range type games. I'm pretty sure I've only seen 1 Harry Potter movie, so that is definitely not a prerequisite.