Having read this series out of order (I read the followup novels of the Book of the Short Sun first) gave me an interesting perspective on it, I think.
Some things, I was like, "ah, I wish I had known that" but just as often I thought, "ah, now knowing that makes this more interesting..."
The books tell the story of a young priest in a poor community who, in his efforts to save his church from the development plans of a wealthy crimelord, finds himself reluctantly on the path to greatness...
It's seemingly a simple story, but the complexities of Wolfe's world and his characterizatons catapult it onto another level altogether.
The book takes place on a generational spaceship that the inhabitants have forgotten is a spaceship, worshiping the original builders of the project as gods (as they intended). However, the minor(?) god that Patera Silk believes has given him a vision is known as the Outsider, and, Wolfe implies, may actually be God... The book has strong religious themes, but also has plenty of action, humor, oddities and grotesqueries, and more... good stuff!