After stumbling upon a hidden trove of diaries, New Yorker writer David Grann set out to solve "the greatest exploration mystery of the twentieth century": what happened to British explorer Percy Fawcett. In 1925 Fawcett ventured into the Amazon to find an ancient civilization. For centuries Europeans believed the world's largest jungle concealed the glittering El Dorado. Thousands had died looking for it, leaving many convinced that the Amazon was...