This is a book that has a lot going for it. You get a sermon, a mystery, poker games and lore, a hero who's a former priest, a corrupt small town in the American southwest, a noirish sensibility, and some darn good writing. So why's the book forgotten? Don't ask me. It's not even available from any of the usual sources on the Internet, though you can pick up copies of Thackrey's nonfiction titles like Gambling Secrets of Nick the Greek and the sequel to Preacher, King of Diamonds (though it's not cheap). If you happen to run across Preacher, it would be well worth your time to pick it up. After you read it, maybe you could sell it on eBay. I'm keeping my copy, though.
There's some very interesting stuff about Thackrey here.
Update: I should have looked more carefully. It's easily available, and it's cheap.