John Crace in the Guardian:
The opening sentence of their new book, The Spirit Level, cautions, “People usually exaggerate the importance of their own work and we worry about claiming too much” – yet by the time you reach the end you wonder how they could have claimed any more. After all, they argue that almost every social problem common in developed societies – reduced life expectancy, child mortality, drugs, crime, homicide rates, mental illness and obesity – has a single root cause: inequality.
And, they say, it's not just the deprived underclass that loses out in an unequal society: everyone does, even the better off. Because it's not absolute levels of poverty that create the social problems, but the differentials in income between rich and poor.