State of Decay is available through the digital distribution platform for a straight-up $19.99. If you're curious about Undead Labs' maiden game, then check out our hands-on coverage. The game was a huge hit on the Xbox and hopefully will be followed by an MMO set in the same world. Undead is also preparing the first DLC for State of Decay called Breakdown that will come to both the PC and Xbox.
[Thanks to Soren for the tip!]