The History of the Byzantine Empire from 765 to 1057 A.D.

George Finlay was a 19th century historian who wrote a number of books about the Middle Ages, including this one about the middle stages of the Byzantine Empire around the times of the Crusades. From the beginning: 
 
“The institutions of Imperial Rome had long thwarted, the great law of man’s existence which impels him to better his condition, when the accession of Leo the Isaurian to the throne of Constantinople suddenly opened a new era in the history of the Eastern Empire. Both the material and intellectual progress of society had open deliberately opposed by the imperial legislation. A spirit of conservatism persuaded the legislators of the Roman empire that its power could not decline, if each order and profession of its citizens was fixed irrevocably in the sphere of their own peculiar duties by hereditary succession. An attempt was really made to divide the population into castes. But the political laws which were adopted to maintain mankind in a state of stationary prosperity by these trammels, depopulated and impoverished the empire, and threatened to dissolve the very elements of society. The Western Empire, under their operation, fell a prey to small tribes of northern nations; the Eastern was so depopulated that it was placed on the eve of being repeopled by Slavonian colonists, and conquered by Saracen invaders.”