The book describes racism in the united States as an aspect of a caste system- a society-wide system of social stratification characterized by notions such as hierarchy, inclusion and exclusion and purity. Wilkerson does so by comparing aspects of the experience of American people of color to the caste systems of India and Nazi Germany, and she explores the impact of caste on societies shaped by them and their people. Caste describes the United States from the arrival of the first enslaved people in 1619 to the current covid-19 pandemic to explain the nature and consequences of inequality.