This game is the rarest of creatures, a high budget immersive sim that refines the formula of past classics such as System Shock 2 without dumbing it down to appeal to a mass audience. It's essentially System Shock 3, and any fan of the genre should play it without hesitation.
Like System Shock, it takes place on a space station where things have gone horribly wrong. The interior and exterior, both fully explorable, are modeled beautifully with modern high resolution graphics and level design. It encourages creative exploration by giving the player a "glue gun" which can be used to create your own walkways along any surface, allowing you to reach areas of interest that you might see while exploring, or to sneak past tough encounters.
Combat is fast paced and challenging, at least for the majority of the game. Weapons each have strengths and weaknesses--- there's no rocket launcher to blow everything up with or sniper rifle to kill everything from a mile away. You'll have to think about what is best for each situation.
Cleverly, all loot in the game is valuable as it can be recycled into crafting materials and then turned into a variety of useful items, including upgrade points. Characters can be built in a variety of different ways to focus on combat, fitness, psychic abilities or skills like hacking and repair.
There game has a waypoint system that directs you where to go, but it's not obnoxious and can be disabled if you prefer. In many cases, the game will provide you with bits of information that you can use to create your own goals, rather than telling you what to do. For example, you might read an email that mentions someone, then use the nearest security station to locate that person and then rescue them or obtain their loot.
There is a lot more I could talk about, including the story which is interesting and contains some good twists. But since I'm running out of room, I'll just say it's a 10/10 immersive sim, absolutely one of the best ever made.