The Shack, the story of a sad-sack Oregonian who meets God, was self-published by William P. Young in the spring of 2007. A year later, it had sold about 1 million copies. An excess of 10 million copies are in print today, and—strangely, in a marketplace where most successes have a bottle rocket's flight path—nothing, so far, has dropped back to Earth. As of this writing, The Shack has spent 105 weeks on the New York Times best-seller list and ranks ahead of Malcolm Gladwell's Blink and Sarah Palin's Going Rogue on Amazon. It dominated this spring's list of the Kindle's most-often-highlighted passages. If you happen to be seeking proof of divine intervention in the publishing business—which, by the way, could use it—there is little reason to look far beyond the raised-type, high-gloss cover of William P. Young's bizarre debut....