But what happened in that brief era is a story worth telling, and in “ American Midnight ,” the historian Adam Hochschild, celebrated for his “ King Leopold’s Ghost ” and other volumes, recounts it with verve and insight. “It is,” he tells us, “the story of how a war supposedly fought to make the world safe for democracy became the excuse for a war against democracy at home.” Between the story of the doughboys of World War I and the glittery onset of the Roaring Twenties is a brutal chapter of American history almost always omitted from high-school textbooks...