From the update:
Hello backers! Mr. Black here, and today I have a very special update for you.
First up, here is a direct link to the Prototype XenoShyft Rulebook! Please note that content has been changed to reflect current Kickstarter inclusions, and ALSO note that it's not the final version, so some content may be moved around, some of the card references may change, may be a few typos left to correct etc etc.
It does however show you the rules of the game and how everything works, like a good rulebook should :)