This book is a key read for Braver Angels interested in how the U.S. became so polarized, and what’s keeping it that way. Klein says the American political system is beset by a feedback loop: “to appeal to a more polarized public, political institutions and political actors behave in more polarized ways. As political institutions and actors become more polarized, they further polarize the public.” Klein combs through the research and presents fascinating, if depressing, findings, such as that the more knowledgeable we are politically, the stupider we become, because people reason to get the answers they want rather than the correct answer. He recommends reforming the political system so it can function amid polarization, such as bombproofing, including doing away with the debt ceiling so that members of Congress can’t regularly push us to the brink of default.