These are fiction rather than NF, but Michael Ennis'
Byzantium is a historical novel in the grand romantic epic tradition, and gives a great picture of the city at the time of Empress Zoe. It's the story of 11th century Norse king, Harald Hardrada, focusing on the time he spent as a member of the Varangian Guard in Byzantium. And Tom Harper's
Demetios Askiates trilogy tells the story of the First Crusade from a Byzantine POV- very good.
Then there's Richard Blake's bravura adventure set in 7th century Constantinople at the time of the Emperor Phocas,
Terror of Constantinople.