This entry in the Casca series is set in an interesting but often overlooked period, of the last major conflicts between the Byzantine and Persian empires before the armies of Islam emerged onto the scene.
The background to the novel is the Persian conquest of Syria and Egypt in 616-619 AD, and the Byzantine recovery in the next decade. Casca and Ayesha are captured by his arch enemies during the Persian occupation of Alexandria. Casca's enemies, the Brotherhood of the Lamb, have lost their holiest item, Casca's spear, to the Persians, and they blackmail him into retrieving it for them.
Casca attempts to achieve this by joining the Roman army that restored the Empire's eastern borders in the 620s. This was not a rapid campaign, and the plot of the book is thus spread over several years.
Roberts has given a good impression of the changing nature of the Byzantine world, as the last elements of Latin Rome live faded away to be replaced with Byzantine Greek. There are some nice plot twists, and the battle scenes are well portrayed. This is another entertaining entry in this series.
The book is also available from the Casca Website