From the back of the book:
Pilgrims on the Luminous Path
The nobles may rule the secular lives of the Known Worlders, but the Church guards their souls — and in so doing, dictates to the nobility. Few lords dare to defy the will of the Patriarch and his bishops. But the Church's rock is not as stable as it once was — new sects and orders have appeared in the wake of the Emperor Wars, shifting the populace's loyalties and reawakening ancient heresies. While the Church stands united against the nobles and guilds, they feud within their cathedrals, vying for dominion over the faithful.
Herein are detailed the lives of the saints, the histories and beliefs of the major sects of the Church, the heretical Incarnates and the religion of the Children of Zuran."