Like Graves' better-known works I, Claudius and Claudius the God, the book has been written by laying down as much detail as is historically known about Belisarius, and then filling in the gaps with credible fiction. As the Claudius books were based upon, for example, The Twelve Caesars of Suetonius, among an extensive bibliography, Count Belisarius is based on the History of Justinian's Wars and the Secret History of Procopius.
Although the books based on Claudius use an autobiographical style, this work purports to be a biography written by Eugenius, a eunuch servant of Belisarius' wife Antonina. The novel covers the entire life of Belisarius, with the bulk of the text devoted to accounts of his life while on campaign in North Africa and Italy. Antonina was often with him during these years, and Graves uses stories about her connections to the court of Justinian and Theodora to incorporate political intrigue and other information into the story of Belisarius' military exploits.
Graves' treatment of Belisarius is mostly respectful: the general is, if anything, hampered by his rigid code of honor and loyalty to his emperor. Other primary characters do not fare as well. Antonina and Theodora are presented as extremely intelligent, savvy, and capable individuals who are nevertheless prone to holding grudges and jealousy. Justinian is portrayed as intelligent but feckless, a tragically poor judge of character, and a spendthrift (even if driven by genuine piety).