For myself at least where I live, they tend to be targeted at older men and women trying to reconnect with religion when they're vulnerable around the midlife crisis age. Most "religious right" are purely single choice voters that just happen to care about money the exact same way a libertarian would. The only difference is they think a God divinely gods them as opposed to an atheist who does not.
Almost all of these books are written by a lay person who basically parrots back interpretations or speeches from bishops, preachers, etc. They literally add no value to the system. They just milk an audience to be frank. You wouldn't read "The simple of of not giving a Fuck" would you? Likewise now, if you say on the title "Turning the other cheek" and put a picture of Jesus walking with a child on a beach and now you've got 99.99% of the christian self help books.
The funniest thing that comes to mind is it's no different than the South Park episode "Christian Rock Hard" where Cartman starts a christian rock band. All he does is rewrite already made songs but add some christianic sayings or phrases. That is entirely that industry. They don't tell you anything new or something you can't just search on some forums anymore.