Action, puzzle, mystery and dark setting all in one.
I mean, you have a god of war/DMC action + portal like puzzles which are combined in a really good way. Designers made an almost perfect balance between those two; You have fast and very dynamic fights all over the place, but just when you reach your berserkering climax the game puts some intriguing puzzle upon you.
Some say that characters in this game aren't deep enough... I don't agree nor do I disagree on that. If you ask me, I liked all the characters. Their look, appereance, the way they talk, walk, fight... everything is good (and some of them really made a great impression on me, like Vulgrim, Watcher and of course Samael).
All in all, a really great game which covers action and adventure genres with a little bit of grim atmosphere.