A historical fiction, looking at the eruption of Mt. Vesuvius from the eyes of an engineer, Marcus Attilius.
It's kind of a mystery (but hard to really think of as a mystery since all of us know what happened to Pompeii and Herculaneum) that the engineer gets to piece together after trying to discover why it is the water is not flowing along one of the great Roman aqueducts. There's also a bit of some drama regarding local politicians and crooked people.
I am a huge fan of novels featuring the Roman empire, and this book has been on my to-read list for a long time and seemed really exciting since I've liked anything about Pompeii since I saw the exhibition of Pompeii come through the Natural Science museum when I was a kid (complete with the casts of the victims of the disaster that were left in hollows in the flow).
Harris does a great job of research, using contemporary sources along with classics, such as Pliny. It's a decent solid historical novel, just not very exciting or compelling.