The geography and history of the minorities living under Islam is the subject of a new book by the noted French scholar Xavier de Planhol. This article sets Planhol's work in the context of 14 centuries of Islamic rule over non-Muslim groups. Islam itself was initially the religion of a minority, a fact that helped determine its treatment of Jews, Christians and some other groups as tolerated ‘Peoples of the Book’. Islam conceived of a society in which non-Muslims had a place, as second class citizens, whereas medieval Christendom saw the Jew or Muslim as an outsider who could not be part of society in a real sense. For the Jews in particular, the meeting with Islam was enormously stimulating, and occasional derogatory remarks about Jews, or bouts of persecution, bore no comparison with western anti-Semitism.