From the back of the book (translated from German):
Angel against heretic. Swords against cannons.
The warriors of the Holy Mother Church wage war against a culture that is even stranger to them than they had expected. This book invites you to explore the British isles – either as a pious Angeletic, or as a ghost-worshipping Briton. Furthermore, the abilities, powers and the history of the fallen Order of Sarielites are finally unveiled in this book. De Bello Britannico describes the battles and the course of the Angeletic conquest campagin, and contains all information you need to join in this historic events together with your group – as an Angel, Templar or steadfast islander.
The war has started. Who will triumph?