Since the original publication of more than a decade ago, the title has entered the vocabulary of businesspeople, policy makers, engaged citizens, and consumers everywhere. The book has given rise to more than 400 “nudge units” in governments around the world and countless groups of behavioral scientists in every part of the economy. It has taught us how to use thoughtful “choice architecture”—a concept the authors invented—to help us make better decisions for ourselves, our families, and our society. Now, the authors have rewritten the book from cover to cover, making use of their experiences in and out of government over the past dozen years as well as an explosion of new research in numerous academic disciplines. To commit themselves to never undertaking this daunting task again, they are calling this the “final edition.” It offers a wealth of new insights, for both its avowed fans and newcomers to the field, about a wide variety of issues that we face in our daily lives—COVID-19, health, personal finance, retirement savings, credit card debt, home mortgages, medical care, organ donation, climate change, and “sludge” (paperwork and other nuisances we don’t want, and that keep us from getting what we do want)—all while honoring one of the cardinal rules of nudging: make it fun!