Samuel Langhorne Clemens, known to America and the world as Mark Twain, is one of the most loved and read men of American letters. Especially noted for his novels The Adventures of Tom Sawyer (1876) and The Adventures of Huckleberry Finn (1884), which examined the innocence and adventure of growing up in America's heartland, Clemens is often presented as a kindly, white-haired man with a gentle smile behind his broad mustache and a genial, unassuming wit. That was, for a time at least, the image of Mark Twain. The Samuel Clemens of real life was a complex, guilt-ridden, and at times bitter man who scorned the pretensions of his Victorian age while trying to live up to them. He was a shameless self-promoter; he constantly worried about money and tried many nonliterary and usually unsuccessful schemes to get it; he sought the approval of America's literary elite and often did...