Based on a college class Kruse and Zelizer (both history, Princeton Univ.) cocreated, this book is a concise, riveting, and carefully argued chronicle of the last four decades of American history, from Watergate through President Donald Trump's first year in office, with the September 11 attacks as a pivotal moment. Many of the recent events described throughout have both a vague familiarity and, in the authors' expert hands, a surprising newness. The book draws its structure and title from four dividing lines in American society: politics, economy, race, gender, and sexuality. Making judicious use of primary and secondary sources, the authors argue persuasively that changes in the way Americans communicate and receive news, along with other broad trends, have made those divisions more pronounced and deep seated. Kruse and Zelizer effectively summarize massive social movements and developments—e.g., the rise of the religious right or the growth of social media—in a few pages. They rightly dwell at more length on the historic 2016 presidential election and its aftermath. VERDICT This highly readable, compelling book should be required reading for all Americans of voting age.—Christopher Myers, Lake Oswego P.L., OR