Mark Twain conquered almost every challenge that came his way except old age. Living well into his seventies, he was a printer, an investigative journalist, a riverboat captain, a government functionary, a bestselling novelist, an imperialism-defying political essayist, a successful playwright and a devoted father and husband. He travelled the world giving lectures that made him many fortunes, which he often used to replenish the fortunes he lost from his madder and most poorly managed investment schemes, such as the Paige Compositor, a self-justifying printing press which worked briefly for a few days in 1894 and then, just as mysteriously,...