Agent of Byzantium is a collection of short stories by Harry Turtledove, centred around the exploits of the eponymous Basil Argyros, a Byzantine secret agent. The stories are set in an alternate 14th century, where Islam never existed and the great ancient empires of Byzantium (the Eastern Roman Empire) and Sassanid Persia survive.
Read more about Agent Of Byzantium: Setting, Stories and Publication History, Reception, Differences