Absolutely fantastic game. For me personally a strong contender for game of the year for sure. But it's not for everyone. If you see screenshots you'll think FPS, but that genre label really does it injustice. It's basically in a direct line with System Shock 2 and Deus Ex. First person RPGs with a strong focus on exploration and narrative. The gunplay isn't even very good and the game also doesn't hide that fact. Heck there are only 3 different guns that just directly do damage. Instead the loadout is filled out with stuff like 5 different grenades with very specific purposes or a nerf gun that shoots rubber arrows. Ammunition is also very sparse so you'll often rather consider to find ways to sneak past enemies or make the environment work for you.
The game is about an alien force taking over a space station (okay yeah, they really liked System Shock 2, but how can one not?). And the station might just be the best designed environment in a game to date. It's not just huge, the attention to detail is absolutely mind blowing. Every single room on the station has a logical purpose. Every single body on the station has a name, a workplace and an office or a room to sleep in somewhere on the station. You can go through the crew manifest and search and account for every single one of them (there is even an achievement for that). There aren't just random bodies sprinkled through random corridors that were put in some arbitrary sequence to unleash enemies on the player. It's a snapshot in time of a simulated space station basically. It makes exploration so very rewarding and unique. And it's not just the inside of the station, you can also go outside in a space suit and see how it all connects as a big picture or you can look behind the walls so to speak and go into the crawl spaces and maintenance spaces between the rooms, into the guts of the station. It's so immersive and cool.
Best of all, they even found a way to make it worthwhile to explore every nook and cranny gameplay wise too since the game has a fantastic loot system. Anything you can pick up is useful somehow since you can put it into a replicator to disassemble it and then use those ressources to make upgrades or ammunition.