Mr. Doherty is improving his storytelling, characterization, and writing style with every novel he writes. This was a solid, thrilling novel with well-rounded characters. Pavo and a vexillatio [detachment] from the XI Claudia are given the mission to infiltrate Persia and to return with a certain scroll, a copy of a treaty made by Emperor Jovian and Persia years before. This treaty may possibly save the Roman Empire from invasion. Pavo and his group enter Persia, undergoing hardships, trek across a hostile desert, skirmishes, treachery, slavery. After a remarkable escape from slavery, the men are poised to recover the scroll. Will it be as valuable as made out? And will the men return safely to Antioch and put it in the hands of Emperor Valens?
The Sassanid Persian setting gave a different flavor to the story. I enjoyed learning a bit about this culture and Zoroastrianism. I like that Pavo does note in one place: although there are evil people bent on destruction of the Romans, there are good, kind Persians he meets, also, to balance out. The archvillain does get his well-deserved comeuppance, and how! I was very impressed with the episode of the whole trek through the desert, with the vivid description of the sandstorm and of the privations the men suffered. The Persian adventures were really exciting. Description of life in the salt mine was well done. The escape from the salt mine was almost miraculous, but the later ones were a bit incredible. I enjoyed the vivid description of the Persian 'Blood Games'.
I wasn't able to put this book down once I started reading. Historical research was impeccable. One thing niggled at me somewhat. I felt choice of expressions sometimes were strange and repeated too often, e.g., someone downing his helmet; someone was grappled by his throat; someone spoke in jagged Greek.... Maybe these were British usage or colloquial in the area in the U.K. the author comes from and I'm not used to them. Perhaps the author could have consulted a thesaurus more often. Other than that, the novel is a fine addition to Roman military fiction in the later Empire.