This fantasy is an epistolary novella, told entirely through the letters written between Nicephorus, the young and recently crowned ruler of the Vesani empire, and Phormio, an old school chum who has been sent to the embattled frontier more for his loyalty to the embattled emperor than as a result of any personal qualifications.
As is apparently in keeping with Parker's other fantasy works, this is more of a historical fantasy about an alternative world without magic, strange creatures, or wondrous landscapes. It's a highly political story, focused on the machinations of individuals in an old, corrupt imperial bureaucracy trying to acquire or preserve power and authority. And it is ultimately a tragic story of friendship, youthful idealism, and betrayal.
The conceit of telling the story through letters works well because the letters themselves are typically brief and to the point. There are some twists and turns that gave themselvs away a bit earlier than I would have liked, but the development of Phormio and Nicephorus's characters is handled well, with little bits of their backstory emerging.
The setting felt odd to me: clearly everyone is fighting at a high medieval level, with armor, swords, and so forth. Yet there are sections in the story where it is made quite clear (in fact, it is key to the plot) that there is a rather sophisticated record-keeping apparatus in place within the empire, to the degree that every piece of armor mass-produced by certain companies receives its own lot number. And books seem to be quite commonplace, at least among the elite. There are references to specific editions of multiple works and of texts updated over decades. All of this lends a somewhat more modern feel to what is otherwise a lower-tech society. I'm not sure how well it works; at times it felt anachronistic, even given that this is a make-believe world.
On the other hand, it did make me want to check on whether the Roman Empire or one of the Chinese dynasties employed such detailed and well-organized record-keeping for military matters.
I wouldn't spend the $20 or so to buy a hardcover of this novella; it's just too slight of a story for that sort of outlay unless you are a big K.J. Parker fan (this is the first of her books that I've read). However, the story is well worth reading if you can find it at the library or perhaps someday included in an anthology.