Kelly starts with a history of both the plague and of the trading routes along which it spread and I enjoyed the first few chapters. When he began to follow the plague from country to country, though, the book became less interesting. At points, Kelly bogged down in the minutia of probating wills where the inheritors had all died, and then he abruptly moves to another part of the country or to a new country altogether. While it must be difficult to reconstruct an epidemic among a largely illiterate population seven centuries after the fact, I think one more pass by a good editor would have improved the flow of the book.
I was also a bit put off by Kelly's attitude in a few places. Kelly used a somewhat clinical tone to describe the history of the plague bacillus and its spread from Asia into Europe and through Germany and France. His description of the Italian and English reactions to the disease, however, made me think of E.M. Forster's civilized, rational English and primitive, emotional Italians and it felt rather condescending. Still, I'd read more of Kelly's work, especially if he were to expand on his final chapter on plague deniers, modern-day scholars who claim that the Black Death was not actually plague but some other illness.