I've been following the development for close to a year now.
It's an open-world sandbox type game, mostly about survival and management. Manage food, termperments of people, supplies, locations, etc. There is a storyline you can follow, but you don't have to. There are lots of random events that happen and things that will change everything. You play as all the survivors you've gathered, and if one dies you switch to another. Personailities play a big role in the game.
There is no multiplayer - the next game they're making will probably be an MMO, but they're doing this first to test the waters and see how well it goes. ANd probably also earn the money they need to make it.
Go check out the site at Undead Labs [http://undeadlabs.com/news/].
