The Secret history should be considered gold standard of insider exposes - and it happened to be written nearly 1500 years ago. Combining wit, insight, gossip, mudslinging, invective and polemic, Procopius, one of the scribes under the legendary Byzantine general Belisarius wrote a biting account of the failings and imperfections of the most powerful men and women of his time, starting with his boss and his wife and working his way up to the emperor Justinian and his wife Theodora. Justinian is credited with bringing about the 'Golden Age' of Byzantium but as Procopius shows, the gold was merely plated on and it happened to be fool's gold. Justinian's reign saw the recovery of lands lost in Italy once the Western Roman Empire fell to the Goths, however, Procopius shows that most of these victories were hollow - the empire expended money and efforts to usually fight its adversaries to a stalemate and then made no effort to integrate these lands into the empire, leaving them vulnerable to reconquest. In Procopius' account, the villain of this piece is the autocratic Justinian, who saw himself as an absolute monarch ruling by divine right. Procopius shows that for all his piety and ambitions, Justinian was a poor and incompetent ruler who centralized power, imposed harsh taxes to fund his wars, induced 'barbarians' to attack the empire by buying them off with bribes thus encouraging other tribes to do the same and undermined all institutions of governance. His accomplice in all this was his wife Theodora, a former prostitute with whom Justinian was infatuated. Between the two, they patronized different church factions, Hippodrome gangs and formed an imperial clique of insiders who were accountable to none and had unbridled power. Procopius provides salacious details of the sex life of his protagonists and heaps abuse on them - calling Theodora a 'bitch' and Justinian a demon. At times his critique is biased and at other times clearly exaggerated but no one can deny the underlying insight into how the empire was being effectively hollowed out by the policies of the dictator in charge.
As great as the core book is, this commentary by Anthony Kaldellis is a fantastic addition which provides lots of helpful context and identifies many of the cross-references between the Secret History and Procopius' other works. The introduction is a great help before delving into the core text as it supplies the background of the work and the circumstances in which it was written and also has sections on the reliability of Procopius as a historian.
In summary, both the source material and the commentary around it are fantastic and I would imagine that a lay reader without a substantial background in Byzantine history would struggle to make sense of the text without Anthony Kaldellis' helpful notes. This book has much more depth than the titillating accounts of sex and debauchery for which it is famous and it would be a shame if readers miss out the fundamental criticism of Justinian's reign and policies, for as the author says, it is probably the lasting legacy of this book alone which has prevented posterity from referring to this emperor as Justinian 'the Great'