There's a long and largely positive review (by Claude Fischer) of The Spirit Level  by Richard Wilkinson and Kate Pickett in the ever-excellent Boston Review. Fischer welcomes the enthusiasm and commitment of the authors to social justice. He is somewhat critical of their argumentation, however. This is the nub of his critique:

“….[I]f the authors took their analysis literally, they might suggest
direct manipulations of inequality: send the richest people—or, probably
more efficiently, the poorest people—out of the country or the state.
Inequality would go down and well-being would go up. Alternatively,
leave the inequalities as they are, but devise ways to hide them from
people—censor the media, say (no more Lifestyles of the Rich and
Famous)—so that people do not know their relative positions. That
should, according to The Spirit Level, bring down crime,
disease, obesity, and so forth. The authors do not go in these
directions, and these are, of course, not plausible solutions in a
democratic society. But they are the logical implications of The
Spirit Level’s explanation.

There are more productive avenues they might have considered. The
authors eschew economic growth to lift the poor because their data
suggest that national wealth is not as critical as national inequality
in affecting health, because growth might preserve or even expand
inequality, and because growth violates their green principles. Further
economic development in developed nations, they assert, is an exhausted
route to greater well-being. Most economists, I am sure, would disagree.
Most politicians, I suspect, would consider the dismissal of economic
growth a wrong-headed strategy for electoral victory.”

Still, he's kinder about the book than I was on this blog, or John Kay in the FT. I thought it was great as political polemic and very weak on statistical evidence.