Our guest is the award-winning British author and journalist William Atkins, whose new book -- a dense and engrossing blend of history, memoir, geography, and travel writing -- is called "The Immeasurable World: Journeys in Desert Places." It's a work that, per The Wall Street Journal, "courts comparisons with the capaciously learned nature writing of John McPhee. But there's also an open-ended spiritual quest to Mr. Atkins's sojourns, which follow closely in the footsteps of religious and