I'm not sure if posts like these are allowed on Tildes and I usually don't do those but Prey is one of my favorite AAA games of the past decade so I couldn't resist posting. It's crazy they're giving this out for free!
Basically, this is System Shock 3 in anything but name. It has all the FPS/RPG elements, the space horror and enough new ideas (which I try and not spoil but any trailer/review should give you a taste) to make it more than just a nostalgia trip. I can really, really recommend it to people who are looking for a big game with lots of ways to play and intense emergent gameplay. Newer games in a similar style include Bioshock and Dishonored, so if that's something you like definitely check it out!