Recommend good PC games with these qualities...?

Amnesia: The Dark Descent. It is awesome and fits every quality you mentioned. The only true flaw in it is the voice actor. Other than that its a puzzle, mystery, non-linear, mature, horror game and I loved it to death. To get the most out of it you should play in a dark room with headphones. a href="http://www.amnesiagame.com/#main" rel="nofollow"http://www.amnesiagame.com/#main/a