Very good game, 90% of what I expected. Having a lot of trouble finding something to compare it to. Its certainly nothing at all like STALKER, except for some textures and models. Lots of people seem to be comparing it to Bioshock, and I can see why, but no Bioshock was more open (believe it or not) and more action-oriented.
Lots of mild horror (I hate horror films but liked this game). Lots of mood scenes – for the love of God read up about “Metro 2” before playing this game. Lots of areas that you navigate with at least one companion, which makes for fantastic situations, as the advanced graphics allow for gunfire smoke buildup, sonic concussions, wet blood impacts etc, so when 4–5 people are all going full auto on their AKs the atmosphere after the battle is, well, quite something.
A minor drawback is the length – this game is real short. I haven't counted hours, but it took me only 3 days to complete, and being totally 100% linear there are no “extra” areas to explore to warrant a second going-through.
In all, I would be shouting from the rooftops for you to buy this game except for one thing: the English translation is bad. And I mean real bad, like “Are they talking about the same events?” bad, and really 70% of the atmosphere is lost with English voiceovers/subs (I'm Russian so can judge). Not since the days of Nightwatch have I seen a worse translation effort. So I guess the final, and I suppose somewhat useless recommendation, is run out and buy this right now as long as you can understand Russian >_<.