The River of Doubt-it is a black, uncharted tributary of the Amazon that snakes through one of the most treacherous jungles in the world. After his humiliating election defeat in 1912, Theodore Roosevelt set his sights on the most punishing physical challenge he could find, the first descent of an unmapped, rapids-choked tributary of the Amazon. Together with his son Kermit and Brazils most famous explorer, Cândido Mariano da Silva Rondon, Roosevelt...