Procopius of Caesarea (c.500 - c.565) was a prominent Byzantine scholar during the age of Justinian and is considered the last major ancient historian.
Wikipedia has an excellent entry on Procopius based on an earlier version by James Allan Evans, originally posted at Nupedia. Nupedia was not a wiki. It was characterized by an extensive peer-review process designed to make its articles of a quality comparable to that of professional encyclopedias. Nupedia wanted scholars to volunteer content for free. Before it ceased operating, Nupedia produced 24 articles that completed its review process (three articles also existed in two versions of different lengths), and 74 more articles were in progress.)
Procopius became a legal adviser to the general Belisarius and accompanied him on most of his campaigns through 540. He wrote History of Justinian's Wars. Links to various excerpts of the History (translation by Richard Atwater) can be found on this page.
Dewing translations at Project Gutenberg: Books I and II, Books III and IV.
Best known is his Anecdota or Secret History (translation at lacus curtius and introduction by H. B. Dewing). Print edition: The Secret History (Penguin Classics), translator G.A. Williamson.
Tim Spalding (Isidore of Seville) writes: Like Thucydides and so many others, Procopius wrote the Secret History for posterity. Unlike them, he apparently wrote only for posterity, as general publication during his lifetime would have led to certain disgrace and probable death. In his account, the young future empress was a shameless and insatiable performing prostitute, the emperor a genocidal tyrant; both were, incidentally and quite literally, fiends. It is a strange, vicious, and, at points, borderline-pornographic work… read on
Buildings (de aedificiis), translation at lacus curtius and introduction by H. B. Dewing, is a panegyric presumed to be written at Justinian's behest, however, this work remained unfinished.
Atwater translations of all can be found at Isidore of Seville.
JSTOR (special access required) has an article by the above-mentioned J.A.S. Evans, Justinian and the Historian Procopius (Greece & Rome 2nd Ser., Vol. 17, No. 2 (Oct., 1970), pp. 218-223)
Mr. Evans also has written several books on the era: The Age of Justinian (Roman Imperial Biographies), The Empress Theodora: Partner of Justinian, and Procopius (Twayne's World Authors Series), the latter seriously out of print, i.e., very expensive.
The novel Count Belisarius by Robert Graves (1938) is based on Procopius’ works along with other sources.
