An acceptable and semi-educational thriller set in ancient Roman times, in the few days immediately before the Vesuvius eruption. The surprising strength of the novel comes from the focus on the system of aqueducts that interlaced the region. The main PoV character is a Roman aqueduct engineer, and the story follows him as he follows the disruptions in the water supply that precede the eruption. This aspect of the novel was very well done, and delves into the various reservoirs, stations, pipelines, building materials, fittings, human resources, and methods of operation for the aqueduct system. The whole system is neat and fiddly and beautiful when in motion, and I feel like it could be its own genre of games, just like the various _Trains_ franchises that dot board gaming and computer gaming (actually, wait, Banks might have already done this in Hydrogen Sonata. I forget). The first half of the novel is built around this water system, as the engineer Attilus reasons back from the sudden water supply problems to what might have gone wrong in the system and how to fix it. This would have been a fine technical drama in its own right since the aqueducts are the only water supply for the 200,000+ people in the area, and if the water is disabled for more than ~48 hours absolutely everything will go to ruin. There are a couple of other elements to the story, e.g. a mystery about what happened to the previous head engineer, labor issues, corrupt and cruel local officials, a love interest, etc. But I feel like these elements are mostly there to spice up the more educational/technical parts of the novel.
Then of course there is the second half of the novel where Vesuvius actually erupts. This part is ok? It has a similar structure to the first half of the novel, in that it has some human drama set on top of a thorough exploration of a segment of history. Where the first half went into detail about the aqueducts, the second half reconstructs the several days of the Vesuvius eruption. Assuming that the novel is not just flat out lying to me, I thought this was part was interesting (if not quite as compelling as the aqueduct parts). I'd always envisioned Vesuvius as a sudden blast and then rapid, fiery, death and entombment. Instead there was a full ~24 hour period where the region was being pelted by light pumice stone, basically a heavy and never ending hail storm. People could and did escape Pompeii during this time; nearly everyone who died there did so as a result of this is fine dog. The end came for the city as a result of the second stage of the eruption, when arcs of superheated gas and ash started rolling down the mountain. Due to the vagaries of wind and geology, there were cities on the other sides of the mountain which escaped destruction and more-or-less survived the eruption. Pompeii of course caught one of these waves directly, causing its complete destruction.
Anyway! I liked much of the historical subject matter, and the remainder was perfectly serviceable.