Caste, as Wilkerson sees it, is the bones beneath the superficial skin we call “race.” It is the obdurate set of assumptions and expectations buried so deeply in human experience that it is all but impossible to excise. Wilkerson identifies the shared features of the caste systems in three countries—Nazi Germany, India, and the United States—exploring their basis in divine will or natural law, the ways in which caste is inherited, the limits on marriage between caste groups, and the rigid occupational boundaries that caste imposes. Nazi Germany is a poor fit for her thesis, but the argument rests solidly on the other two. Admirers of her earlier book, The Warmth of Other Suns, which dealt with the migration of Black Americans to northern cities during the twentieth century, will recognize her passionate prose, laced with gasp-inducing stories. Readers may not ultimately be convinced that caste and racism are different, but they will come away with a new understanding of systemic racism in the United States, a deeper appreciation of the banal but no less painful wounds it inflicts daily, and a grasp of what it will take to loosen its grip on American society.