Amid mounting fears of violent Islamic extremism, many Europeans ask whether Muslim immigrants can integrate into historically Christian countries. In a groundbreaking ethnographic investigation of France's Muslim migrant population, Why Muslim Integration Fails in Christian-Heritage Societies explores this complex question. The authors conclude that both Muslim and non-Muslim French must share responsibility for the slow progress of Muslim integration. Claire Adida, David Laitin, and Marie-Anne Valfort found that in France, Muslims are widely perceived as threatening, based in large part on cultural differences between Muslim and rooted French that feed both rational and irrational Islamophobia. Relying on a unique methodology to isolate the religious component of discrimination, the authors identify a discriminatory equilibrium in which both Muslim immigrants and native French act negatively toward one another in a self-perpetuating, vicious circle. Disentangling the rational and irrational threads of Islamophobia is essential if Europe hopes to repair a social fabric that has frayed around the issue of Muslim immigration. Muslim immigrants must address their own responsibility for the failures of integration, and Europeans must acknowledge the anti-Islam sentiments at the root of their antagonism. The authors outline public policy solutions aimed at promoting religious diversity in fair-minded host societies.