A story of the Roman empire with a focus on the role of climate and disease in the fate of the empire, or rather their role in constraining the course of development of the empire.

The book covers three pandemics and a few climate shifts, as well as a multitude of smaller epidemics and disease outbreaks, and stands as a superb example of how to use science in history writing. Harper introduces a lot of objective evidence, from tree rings to bone lengths, and he's very good at showing where the evidence points, as well as explaining when there are gaps in the record and things we do not know.

It wasn't the book's main focus, but the book also made me realise just how far east and south Rome and its influence stretched, with evidence being provided that Rome and China knew about each other. Similarly it helped me remember just how long Roman influence in the mediterranean lasted: the last subsidized grain shipment from Alexandria to Constantinople was in the 7th century, and much of the middle east and northern africa was still linked to the byzantine empire until the islamic conquests!