I'm heavily addicted to playing now. I haven't got this into a single player game in years. There's elements that are a bit witcher-ish, or almost lara croft like. Moving around an open map of hogwarts and surrounding areas is like a childhood dream.
What they've done with the building detail and map detail is seriously beautiful. I barely played the actual questline for a while because I was so wrapped up exploring.
For those that aren't too upset about the Rowling controversies, there are some really lovely cross-overs between specific details you find in the books, vs the films. I'll leave no spoilers, but if you read the books, there'll be some stuff in there that comes from them.
The combat is also pretty fun, with gear of different stats, ability bars, combat potions and healing potions. It's got the works for a good RPG. Plus some extras.