''[Black Southerners] did not cross the turnstiles of customs at Ellis Island. They were already citizens. But where they came from, they were not treated as such,'' writes Isabel Wilkerson in The Warmth of Other Suns, her sprawling and stunning account of the Great Migration, the 55-year stretch (1915–70) during which 6 million black Americans fled the Jim Crow South. Wilkerson, a Pulitzer Prize-winning journalist, uses the journeys of three of them a Mississippi sharecropper, a Louisiana doctor, and a Florida laborer to etch an indelible and compulsively readable portrait of race, class, and politics in 20th-century America. History is rarely distilled so finely. A

