This really is an amazing game, and if you haven't tried it then go out and get it now. I love the art style, the humour, and the gameplay is just fantastic.
I'm surprised more people haven't said Minecraft. What with all the mods, texture packs, and the directionless gameplay, it has nearly infinite replayability. Not bad for the $20 I paid for it.
I've been reading a lot of Lovecraft lately. The language can be a little archaic but some of the stories are quite unnerving. Mountains of Madness has to be my favourite so far.