I don't play it, but is it a good game? It's nominated for a award for the XBox Live Awards.
The Dark souls series brings back the same sense of challenge that games had on the original Nintendo. It's an RPG but it's not the kind of game where you just hack and slash through hordes of enemies and the enemies barely do any damage to you; lots of trial and error before beating every level and boss, every enemy has a reasonable chance to kill you if you are not attentive. Multiplayer is the best part of the game, in my opinion.
people either love or hate the game... you'll find out which one you are after about an hour of playing.