Kinda a screw up I think.. Steam announced it as multiplayer, they've just pulled that statement as.... IT HAS NO MULTI-PLAYER!! Which reminds us of the 1503 release where they promised to add multi-player for 6 months in a patch, and then didn't.
Play the demo for a weekend and that's pretty much all there is to it. Get 1602 if you like the multi-player (which this game was really meant for), it was the last game they made that supported it.