In this richly detailed biography, Lyttle (Ernest Hemingway, 1992, etc.) gives young readers a Mark Twain whose life, like Huck Finn's, was defined by the American paradox: Nearly every experience of freedom came burdened with a sense of responsibility. Seeking a hiding place for the day while ditching school, the young Sam Clemens went to his father's office only to discover a dead body on the floor -- punishment, he assumed, for his truancy. Yet an overdeveloped conscience hardly conquered Clemens's searching, independent spirit. Lyttle chronicles thoroughly -- and with refreshingly little sentimentality -- Clemens's stint as a Mississippi River boat pilot, his travels west as a prospector, and his work as a journalist, from which he gradually transformed himself into Mark Twain. Lyttle carefully notes the complexity of this persona, who played to packed houses with his painstakingly rehearsed, seemingly offhand speeches and who created some of the most lasting fiction in our literature. Lyttle's treatment of Twain's work, however, is stingy by comparison. He covers The Adventures of Huckleberry Finn in only a handful of paragraphs and oblique references (""He continued to read evening installments about the young prince [in The Prince and the Pauper] to his family, but he had too many misgivings to read the Finn story to them""). Still, Lyttle has delivered a superb portrait of the man.