The author of one of the most celebrated books of the past year will Wednesday be at the center of an interview that kicks off the Nantucket Book Festival’s 2021 virtual and live programming. Pulitzer Prize-winning journalist Isabel Wilkerson, whose 2020 book “Caste: The Origins of Our Discontent” has been on the New York Times nonfiction bestseller list for 36 weeks, will sit down for a conversation with NPR journalist Diane Rehm in what festival organizers call “an event we have dreamed of for a long time.” The festival describes “Caste” this way: “Wilkerson argues for a new way of understanding racial inequalities in America through the lens of a rigid caste system. She uses her own personal experience, and also reaches across continents and through history to demonstrate how humans create artificial divisions to justify who has power — and who doesn’t — in a society."