Mark Twain was born fully grown, with a cheap cigar clamped between his teeth. So begins Sid Fleischman's ramble-scramble biography of the great American author and wit, who started life in a Missouri village as a barefoot boy named Samuel Clemens. Abandoning a career as a young steamboat pilot on the Mississippi River, Sam took a bumpy stagecoach to the Far West. In the gold and silver fields, he expected to get rich quick. Instead, he...