After playing this game, not in the recommended setting of dark and loud due to... personal reasons ahem; I found it to be mint.
Starting the game caught my attention and curiousity and I found myself eager to discover what happens next!
To me, if a game is fun, then it has satisfied me and this game was excellent in my oppinion, solid engine, decent A.I. but it's really about the puzzles and stealth anyway and the atmosphere sold it.
If you have a brain and want to use it then this may prove to be one of those games that aren't so chicken as to respect your intellect and not hold your hand (much) during a challenge and be enjoyable.
Patience, thought (logic and analytical abilities) are required; reward, however? Sorry, no shot guns to satisfy that constant blood lust lasthing through the game