Why are people more relaxed and at ease with each other in some countries than others? Is it true that mental illness is three times as common in America as in Germany? And why are children faring worse in some nations than others? The answer to all these questions, suggest Richard Wilkinson and Kate Pickett, is inequality, and here they demonstrate how it affects us individually, altering how we think, feel, and behave. Along the way, they challenge the conception that humans are inescapably competitive and self-interested, and that inequality is the product of "natural" differences in individual ability. Proving that societies based on sharing and reciprocity benefit from much higher levels of well-being, Wilkinson and Pickett lay out a possible path towards them.