The Building of Christendom by Warren Carroll, 547 pages
The second volume of Carroll's History of Christendom opens with the Council of Nicaea and closes with the end of the First Crusade, along the way covering the decline and fall of the Roman Empire, the rise of Islam, the age of Charlemagne, the beginnings of the Reconquista, the predations of the Vikings, and the origins of the great heresies of Arianism, Nestorianism, Monophysitism, and Iconoclasm.
In a Christendom besieged by barbarians, riven by division and social strife, and struggling over theological definitions, Carroll makes it clear that this last was the most important. The far ranging consequences of a Monophysite or Iconoclast victory would have been greater and deeper than if Carloman had ruled and Charlemagne retired to a monastery, or if the Goths had defeated Belisarius.
An excellent retelling of the story of how classical culture was interwoven with Christianity to create the fabric of Western society.