Don't believe the mediocre reviews.
The graphics are exceptional: the environments are immersive, the limbs of the enemies and NPCs are round, and don't look like they are made out of textured blocks. The guns, and other details, are strikingly realistic.
The action is extremely intense. The firefights involve waves of bad guys almost rivalling the numbers of enemies in Serious Sam.
The levels are linear, which I liked, but they are alternate routes through areas that let you make tactical and strategical decisions when fighting enemies. This adds more depth to the action in that you can try different ways to get through areas rather than just run around and try not to take too much damage.
Also, that most things are destructible adds a excitement and realism to the game; you can't avoid heavy machine gun fire by hiding behind a wooden crate, as seems to be the norm in many games. But then neither can the bad guys. And the destructible things don't stand out from the environment; they look just like everything else.
The gameplay is very good, and very fluid. It is a little odd that you can't jump, but you get used to it soon. The screen goes blurry when you reload, so this, like many other things in the game, adds both realism and excitement.
Black adds a lot of new elements to the FPS genre. I highly recommend this game. It is short. But the game is so intense, and so immersive, you wonder if its technically possible to make it longer. And there is so much action that the replay value is very high.
All in all, a truly excellent game.