Morgan and Reid begin by conceding that any history of Islam must cut its subject by period and by region, and that both cuts are arbitrary without being meaningless. Their volume takes the eastern Islamic lands from the eleventh century, when Saljuq incursions mark a real break.

Two developments organize the account. The first is the arrival of the steppe peoples. Turks had earlier entered Muslim society as individually purchased soldiers, valued precisely because they arrived without kin or local loyalties; now whole tribes came, leaders and nomadic order intact. Turkish and Turko-Mongol dynasties then ruled much of the region into the nineteenth century, and no monarch of Persian descent governed Iran between the Saljuqs and Reza Shah.

The second is maritime. Islam travelled the Indian Ocean with Sufi scholars and merchants instead of armies, meeting religious traditions comfortable with many outward forms of one reality, a pluralism al-Biruni had already remarked on.