From Isabel Wilkerson, winner of the Pulitzer Prize in journalism, Caste: The Origins of Our Discontents continues a discernible theme in this year’s awards: books that take a long, hard look at America itself. Wilkerson argues, persuasively, that Americans are mired in an outdated and dangerous hierarchy system that goes even deeper than race and class. The silver lining: It’s not too late for meaningful change.