Graham Greene's career spanned a global stage, with his works set in locales as disparate as Hanoi and Havana, Liberia and Lithuania, Mexico and Malaya. Greene also deliberately sought out hazardous and physically demanding journeys. In Journey Without Maps (1936), his first and arguably his finest travel book, Greene writes, “There are times . . . when one is willing to suffer some discomfort for the chance of finding—there are a thousand names for it, King Solomon's Mines, the 'heart of darkness' if one is romantically inclined, or more simply, as Herr [Kurt] Heuser puts it in his African novel, The Inner Journey, one's place in time. . . .” Paul Fussell, in Abroad: English Literary Traveling Between the Wars (1980), calls this “real” travel, as opposed to tourism, and connects it to its etymology of travail: “travel is work—the traveler is a student of what he sees.” Greene's travel writings are usually thought...