Good but not great Rome-in-space based ambassadorial procedural (is that a even genre?).
The story is propelled by two strengths, a cool and innovative piece of technology and the authors love and mastery of language. The way she makes us think in a made up alien language without leaving English is mesmerising. The technology gimmick is awesome and central to the plot so I wont go further.
Outside of that it felt like a fun but formulaic political murder procedural. Another darker (and more sci-fi) plot grows later in the book and will be even more important in the sequels.
Its very Roman inspired, complete with lots of barbarian and Empire talk, with small changes it could be simply set in the time of the Caesar's, and while the main technology item is well thought out and very impressively rendered, there is not so much else to inspire. The plot is complex and gripping for the most part, and it is well worth a read!