This book is part of a 10-book set that comprise the core rules. Book 6 should contain information for GMs -- currently, it is a themed notebook for GMs to make their own notes.
Note that these "books" are intended to be printed on a single sheet of US letter paper and folded in the PocketMod format.
from the author's blog
Adventures in the New Kingdoms is the setting I’ve been running Fantasy RPGs in for most of my life. The ancient empire of the Kale has collapsed under its own weight and is being replaced by the age of man. Of the three greatest Kale cities, only one still remains within their grasp, the other two being the centres of great human city-states.