It is a survival game, comparable to Minecraft in that you grab resources to craft items with a clear tech tree, but I think the similarities end there since there's little emphasis on building pretty structures and more on not being brutalized by the endless things that want you dead. You play as Wilson, a scientist who is transported to an intensely hostile world, and what you do from there is up to you. The game allows you to simply see how long you can survive (conditions getting nastier as the days go on), with a bevy of parameters to tailor the game to be as hard/easy as your tastes can handle. However, there is also an adventure mode you can trigger by finding a special doorway and going into it. From there, you will face a series of worlds that grow in difficulty up until a final confrontation with Maxwell, the dapper demon that banished you to this hellscape. Don't Starve features perma-death, though dying in adventure mode simply jettisons you back to the "sandbox" mode and forces you to start from the beginning.
The game is currently in beta, and might still be a little lean on features. The devs are updating regularly enough to the point where there's an in-game ETA for the next patch. However, if you buy now, then you get a SECOND COPY FREE! Perfect for the looming holiday season. It's on Steam now, and you can also buy it directly from the devs here. It's also on the Chrome Web Store as a browser game, but I dunno if that's free or also cost money. The game will release April 23rd, is currently 20% off for the low low price of $11.99, has an additional free copy when you buy it, and offers two TF2 items when you preorder on Steam. What a deal!
Here's a trailer if you dig that kind of thing.
FAQ
OH GOD WHAT DO I DO?
Unlike similar games, where night just spawns hostile creatures, night in Don't Starve kills you. After a short period, you will start losing chunks of health until you die or head to a light source. Note that doing the latter will be very difficult since the game is pitch black at night.
So, your first goal is two enough materials for a campfire. You have plenty of time until night, so check your crafting options and get the shit needed for an axe. From there, getting a fire going should be easy. I recommend waiting until after or just before night before making the fire, as it requires fuel to keep going. Oh yeah, it'll need fuel. Grass, sticks, and logs will all do the trick.
I am dying so fast to spiders!
Your next goal is to make advanced stuff that can help you fight back. There are three tiers of science machines that unlock better crap (Science Machine -> Alchemy Engine -> Shadow Manipulator), so you should aim to make that science machine ASAP! Once it's made, you should craft a spear and log suit, increasing your damage over that silly axe and absorbing significantly more damage. While you shouldn't go looking for fights in this game, you should always carry a weapon and armor at all times.
I am going instance please make it stop
Sanity drops at afternoon/night (larger drops when you are in pitch black), exposure to monsters, and using shadow objects. You can increase it by wearing dapper items, picking flowers, eating candy, and killing shadow monsters. You also slowing regenerate sanity during the day.
Empty sanity does not kill you, but it does make your life a lot harder.
My screen is freezing. Why?
It is winter, and your character is cold. Too much freezing around the edges of your screen, and damage occurs. You can only reverse freezing by staying near a fire, but you can delay freezing by wearing hats/vests, carrying warmed heat stones, and growing a beard (if Wilson).