This book of historical fantasy presents a world that can be best imagined if you think about Asia Minor at around the year 700AD. This specificity is possible because of the general topography Hansen creates in the novel. For example one of the main characters, a man of action named Priscus, comes from the Gumlaag Mountains in the east, which can be thought of roughly as the Caucasus. There is also an analog for the Black Sea and the Don River which flows into it from the north. The Don here is called the Dog River.
The other main character, Galen, is a scholarly gentleman who survives the various coups and counter coups of a turbulent period at the end of the Roman Empire (the period the book "covers", although it is actually strictly a fantasy). Galen has links with Priscus but their lives really intersect at the end of the book as a result of an embassy Galen is assigned to carry out to visit the (Muslim) Vled who live in lands located to the north of the Middle Sea. Priscus is assigned to accompany Galen and protect him from harm.
Danger is ever-present in Hansen's pre-Modern world. It is a rough, dirty, unpleasant universe where lives are short and pleasures taken whenever and wherever they can be found. Not exactly the sort of world you'd want to raise a child in but Galen gets married - it is a marriage arranged years before - to the complacent Placidia and they have a son. Fathers and sons form important elements of the plotting in the book, as befits a society where the main social structure is the family (again, it's a pre-Modern society that predates to a large extent the development of what we can recognise today as the State), and where so much in the social order relies upon the peaceful transmission of power from one generation to the next through premogeniture. Not that that is always what happens.
But it's not an entirely prelapsarian world. Priscus, for example, is different from most of his peers in that he spends large parts of his life living in foreign societies. He is multi-lingual and his education has been enriched by exposure to societies other than the one in which he was first raised. Priscus is sort of a modern super-hero: intelligent and strong, violent and uxorious. By injecting a measure of Modern sensibility into the drama surrounding the characters in the book, Hansen gives us a reliable lens through which to view critically the ancient world and also the contemporary world in which we actually live today.
Galen, too, is a modern type of person. Literate and cultured, he is also wise to the power of propaganda and the way that history is written by the victors. In fact it is the "secret history" that his father started and that he is determined to complete - the accurate story of the political system of his time - that ends up closing the novel Hansen has written. There is something here therefore not only for the reader who likes historical fiction (historical fantasy) but also for the reader who likes to be asked to think a bit more deeply about how things are. Of course, some might object to how that dichotomy is formulated.