Book excerpt: "Friedrich Heer's incisive history describes how the buoyant, fluid society of twelfth-century Europe solidified into the medieval world - a fourteenth century of religious and intellectual intolerance, fortified frontiers, and bitterly competitive states. he discusses the Crusades; the alienation of Rome and Byzantium; the rising power of the Church and the aristocracy; the life of the peasant, the town dweller, and the tradesman."--Page i.