Richard Wilkinson and Kate Pickett’s The Spirit Level: Why More Equal Societies Almost Always Do Better argues that income inequality is the root cause of many social and health problems. Using extensive statistical analysis, the authors demonstrate that societies with greater economic disparity suffer from higher rates of crime, mental illness, obesity, and reduced social mobility. They argue that beyond a certain point, national wealth matters less than how evenly it is distributed. The book calls for systemic policy changes to reduce inequality, presenting equality not just as a moral imperative but as a practical necessity for societal well-being.