While the entire world knows Mark Twain as the renowned author of many classic American novels, few people are aware that he was also a highly successful businessman. In fact, more than half of his life was consumed by moneymaking pursuits, which often resulted in writing projects being neglected–but at the same time, these adventures were the inspiration behind many of the characters found in his books. In Ignorance, Confidence, and Filthy Rich Friends, Peter Krass captures a little-known side...