This is by the same author that writes about mountain climbing disasters. He wrote Into Thin Air.
Anyway it was fabulous non fiction about extremist religious groups, namely very fringe fundamentalist mormons.
He interviewed a wide variety of people and researched history and used interesting quotes to show a side of society that I don't know much about. And I didn't think I was even interested but Krakower is such a good journalistic writer. I downloaded the free first chapter and was hooked. What a story!