Whew, where to start?
I just finished the game, and it clocked in at 6 hours. Now as a game, especially for 29.99, those are not great numbers. However, as a memorable experience that was like nothing I ever played before? Worth it.
You are playing a story, more a passenger than a pilot. The fights are not deep, but they are fun and very tense with hints of permadeath and save wipes cropping up if you suffer too many defeats. The puzzles are cool, not terribly challenging, but enough to give you some good "AHA!" moments.
The main reward comes in the story and the emotional ride. The main character suffers from several forms of mental instability, but since its back in the Celt days, it all becomes swept into a blanket description of "The Darkness."
This is where this game really hit me personally. I live with Bi-Polar Depression, Severe Anxiety, and mild Schizophrenia. I had to take breaks from the game because it really nailed these conditions in the game. Constant whispers, doubt, mania, self hate, and misleading thoughts plague you the majority of the game. People who don't suffer from these types of conditions can gain an light understanding of what people who do go through on a daily basis. It was rough for me in spots, but overall, incredibly rewarding and a one of a kind ride.