Micha,
There isn't any manual. In this unboxing YouTube video →
http://www.youtube.com/watch?v=h4Ueosdd76U, Daedalic claims (around the 2:00 mark), "It's also a real card game, but here's the clue: You, the gaming community, are supposed to create your own card game."
So I'm assuming that you're just supposed to make up your own rules. :)