The main emphasis of this new book from Luigino Bruni is a praise of heterogeneity, arguing that society works when different people are able to cooperate in many different ways. The author engages in a novel approach to reciprocity looking at its different forms in society, from cautious or contractual interactions, to the reciprocity of friendship to unconditional behaviour.Bruni'ss historical-methodological analysis of reciprocity is a way of examining the interface between political economy and the issue of sociality, generally characterized by 'two hundred years of solitude' of the homo economicus. This historical analysis exposes an absence and this book looks at the reasons why among the many forms of reciprocity present in the civil life economics has chosen to deal just with the simplest ones (contracts and repeated self-interested interactions). The second part of the book is an analysis (with repeated and evolutionary games) of the interactions of the three forms of reciprocity faced with a forth strategy; the non-reciprocity.