A pillar of first-person horror-thriller.
It doesn't have a lot of crazy scares. I had a few moments when I realized I was seen by an enemy and panicked, then proceeded running aimlessly through corridors only to end up cornering myself and being eaten alive. It's good at giving you that rush every once in a while. A few times it even requires you to be quick on your feet, like when a monster busts through a door you thought you had secured. You'll be on your toes for most of the game.
The music and its programming are good. I like the seamless transitions between creeping music and chase music. It works really well to get your blood pumping.
The gameplay does get somewhat repetitive when you realize you're facing the same simple breed of monster for most of the game, which has no variation within itself. You won't need to employ many mixed tactics to survive. The same approach will usually work for everything. This was the worst mark in my experience with the game.
The story is alright. A little vague and a mite cliche', but it works. It would have helped a lot to develop a more unique story.
Recommendation: play it if you like scary games. It's one of the better ones, even if it's not the most original or terrifying. And it's cheap. But make sure to get all three episodes of Penumbra. You need to finish them all to resolve the story.