For a man who liked being called the American, Mark Twain spent a surprising amount of time outside the continental United States. Biographer Roy Morris, Jr., focuses on the dozen years Twain spent overseas and on the popular travel books The Innocents Abroad, A Tramp Abroad, and Following the Equator he wrote about his adventures. Unintimidated by Old World sophistication and unafraid to travel to less developed parts of the globe, Twain encouraged...