Unlike the Iditarod, the Yukon Quest International Sled Dog Race isn't for moneyed adventurers with a fanciful interest in mushing. The race, billed as the toughest in the world, crosses 1,000 miles of forbidding land between Whitehorse and Fairbanks, Alaska, and pits man, woman, and dog against the nastiest that nature has to offer. In "Racing the White Silence," Canadian journalist Adam Killick follows the racers and their dogs for two weeks, taking...