The People of the pocket realm of Brocschtal are simple folk who live as they have for thousands of years. Farming the land, raising sheep, getting in the occasional brawl. And fighting off the infernal attacks of ghouls.
It looks like a cook's book. It is a cook's book. It is also where the cook, who happened to be a master spy, encoded all his secrets and contacts. The book has innocently fallen into your group's hands. Everyone wants it, and many are not subtle or peaceful in their attempts.