Do a quick search for Christian literary agents, and see what they're interested in publishing (same goes for publishers) It reflects pretty much what takes up most of the shelves at the Christian Book store; Junk. I was in the Christian book store the other day browsing the new releases and was struck by the fact that some of the authors of supposed theological books were people who were famous for other reasons, or deserve to be published simply because they manage to fool 10,000 people a week at their mega-church (success is the proof of truth right?). We live in a culture where the man who landed a plane in the Hudson river is a respected aviation expert, (nothing against sully) not because he's an expert, but because he has brand recognition. In Christianity like the rest of the world it seems that brand recognition and loyalty is the major onus behind much that is produced (and a major reason I've started collecting and reading old books). Our current "discussions" are so vacuous and uninformed they're downright incestuous.
I can tell you; if you're a washed up celebrity, becoming "born again" and writing books seems to be a good career move.