Richard Fletcher reminds his readers that the scope of his book is limited, even though the story he is telling is not. An adept historian who writes with clarity and expertise, Fletcher sets for himself the nearly impossible task of relating the complex interrelations between the Islamic and Christian worlds from the 7th to the 16th centuries, focusing on the Mediterranean, but touching upon Northern Europe, Asia Minor, and even on the vast reach of the Mongol Empire. Fletcher describes the establishment of Islam in the 7th century and the subsequent rise of the Abbasid Empire a century later and describes the shift from an Islamic society defined by Arab ethnicity to a ruling power defined by religion and culture. Initially, Fletcher explains, Christians were tolerated (but disdained) in the fast-expanding Islamic world primarily because they provided a link to the ancient Greek and Roman learning their conquerors coveted. However, in less-receptive regions, such as North Africa, Church leaders fled to Sicily and southern France, weakening a Christian presence in those areas. While Fletcher provides many examples of interaction between the two worlds--including diplomacy, pilgrimage, trade, and most obviously, war (the Crusades)--he maintains that these contacts were never solidified by an earnest attempt on the part of these diverse cultures to "blend." In the best of times there was coexistence. In the worst, there was outright persecution. The reversal of Islamic s