A new book by Jon Krakauer, who helped launch the current passion for bestselling narrative nonfiction with Into Thin Air, is about religious extremism in the U.S. It's called Under the Banner of Heaven: A Story of Violent Faith and concerns a double murder in Utah committed by Mormon religious fanatics. Krakauer spent four years investigating the sinister beliefs of a group of Mormon fundamentalists who defy both civil authorities and the Mormon establishment and have created a violent theocracy. Bill Thomas and Vintage/Anchor's Marty Asher jointly bought world, first serial, audio and book club rights from agent John Ware. According to Krakauer, the book "is my attempt to understand religious passion and the terrible things people do in the name of God." It's set for September.