If you want a primer on Wilkinson and Pickett's joint book The Spirit Level, then the pieces here are worth a look (one by me). And for a comprehensive set of responses to their critics, including a pre-emptive strike against Gerry Hassan’s recent piece on OK this is all you need. (It is worth noting too that Wilkinson and Pickett’s work is peer-reviewed; that of their critics isn’t.)
For me as a philosopher, the thing about The Spirit Level that is most exciting is that as a study of the pervasive harms of inequality it strongly suggests that John Rawls's 'difference principle', which says that inequalities are OK provided that they materially benefit the worst off, a principle that has dominated political philosophy for 40 years, is simply wrong. Empirically wrong.