This is a first person puzzle game from the same creators that made the Half-Life series. It's pretty short and can be finished in one sitting but there is a lot of replay value and I believe that it's a good change to play an intellectually challenging game once in a while.
I really don't want to spoil it for you, but there is a very interesting and unexpected turn of events as far as story goes and I simply loved it. This is definitely not the typical dystopian future Half-Life storyline where you're a hero scientist trying to save humanity, but it IS in fact very dystopian and we can see the developers' sense of humor reflected in it.
The only thing left to say is that at the moment the game costs 9.99$ on steam and if you haven't played other Half-Life games, you might as well get the Orange Box which contains all the goodies Valve produced in the recent years at a really good price (I am kind of a Half-Life fan so you might want to get someone else's non-biased opinion on this).
Oh and one more thing. If you're planning to get Portal 2, I strongly urge you to play Portal 1 first, since it makes the story much more enjoyable and you'll understand lots of references and jokes if you do. But more on Portal 2 later.