Short Review
Oxygen Not Included is a management game at its core: you have to take care of your little minions and keep expanding. But you must be careful as they can starve to death, suffocate to death and catch a variety of different diseases and you guessed it: die.
What sets this game apart from all other colony games is the huge replayability factor (every map game can be different) and how many different ways are out there to play the game.

Would I recommend the game?
Absolutely! I have already bought it for two of my friends and they both love it! I'm very excited for the full release.

Long(er) Review
Oxygen not included puts you in charge of a colony, populated by cute little creatures called duplicants. You start in the center of a huge asteroid and start digging. You mine resources and through research you unlock technologies that allow you to make life easier for your duplicants. If you dig up you find space, if you dig down you encounter magma. Contrary to the title Oxygen is not your primary concern. Expect food, diseases and heat from machinery (that would not allow your corps to grow) to be the main causes of failure. You most likely fail miserably and a lot. Experiment with build orders and tweak the difficulty settings. Choose the seed map you want to explore and expand the colony all the way to building rockets. Then travel to other planets to farm them for resources that you can no longer find in your own asteroid. Automate processes and keep your duplicants drinking espresso all day long. (Keep in mind that the game doesn't have a clear winning condition although base sustainability is no easy goal).

I don't remember how I found out about this game. I must admit what drew me in at first was the cute graphics, as I am a sucker for unique art style. I knew Klei studio from their other popular game: Don't Starve, a game I own and have played but I'm horrible at.
When I first loaded the game (this was before rockets were introduced) I was overwhelmed by all the menus/overlays and sheer amount of information thrown at me. I did my best but I watched in horror as my colony spiraled into chaos with no oxygen, food and with duplicants stressed out of their minds peeing everywhere and destroying my precious few buildings... Fast forward to a couple updates ago during fall, when I thought I'd give the game another chance: I haven't stopped playing since.
Personally, I loved being involved in the development of the game and watching it evolve. Klei values players' input and feedback, sadly that cannot be said about all game developers out there. I participated in the beta testing for many of the recent releases and they were quick to fix bugs and address some of the game exploits players discovered. I was pleasantly surprised to even see one of my suggestions being included in the recent release. Many game mechanics have changed and that is expected with EA games. With the release of the Quality of Life Mark 3, the game got an official release date. I feel that now the game is pretty much polished concerning game mechanics. Also, the fact that the game supports mods would definitely enhance player experience.

All in all, I believe Klei put together a superb game that will surely keep you entertained for hundreds of hours!!