Played it for a few hours, and it's... Interesting. The gameplay reminds me a lot of Deus Ex or System Shock, in that you can hack stuff, use "magic powers" via psychic implant whats-it, and blast dudes with various types of guns. Supposedly there are stealth mechanics but I haven't actually tried being stealthy so I can't vouch on whether or not it works. You progress by getting levels, killing enemies doesn't appear to give experience points directly so I assume you get them for certain actions or your performance in doing stuff. The overall quality of action seems decent compared to any other FPS, but there are a few quirks, namely the UI which is rather clunky and the scope animation, which actually makes things a bit harder to see. The 1-9 key weapon selection wasn't working for me either, so that's either bugged or something is going on with my keyboard.
The game's setting is something I don't really know how to describe. The dialog is clearly written by someone that isn't a native English speaker, which can make it a bit hard to really get invested in whatever plot may be there. NPCs speak in a different language completely; I think it's Russian but I'm not exactly the best person to ask about that kind of thing, it could be made up for all I know. Oh also there's co-op. That makes sense considering they're selling a 4-pack. When I checked out the server list, I noticed some of the servers had the "increased_maxplayers" tag. One of them had 19 people in it which sounds very hilarious.