A concise history of Byzantium - Warren T. Treadgold

Between AD 285, when Byzantium first separated from the Western Roman Empire, and 1461, when the last Byzantine splinter state disappeared, the Byzantine state and society underwent many crises, triumphs, declines and recoveries. Spanning twelve centuries and three continents, the Byzantine empire linked the ancient and modern worlds, shaping and transmitting Greek, Roman and Christian traditions - including the Greek classics, Roman law and Christian theology - that remain vigorous today, not only in Eastern Europe and the Middle East, but through western civilisation.
This book examines the causes behind Byzantium's successes, failures and remarkable longevity. The author shows how Byzantine political leadership, military strategy, cultural attitudes and social, institutional and demographic changes combined with the strengths and weaknesses of the empire's enemies to explain the paradoxes of Byzantium's long history.