This book gives a very good sense of changes in how people perceived diseases and the medical establishment in general. It covers 50 pandemics and epidemics in roughly chronological order. Hays acknowledges at the beginning that the focus is on the Western World because that is her area of expertise and that is what she thinks her readers will be interested in.
The book never focuses on any one disease for more than 20 pages, and mostly only have 3-5. But each section does contain a bibliography which can be quite useful.
Each chapter/disease has a section that covers what the disease is, the significance of the disease, how it was understood at the time, remedies, and unresolved historical issues as well as a bibliography and often suggested reading. Some sections also include bits of source material, usually no longer than a paragraph or two.
The book gives a good feel for how diseases are thought of and changing medical, political, social, and often theological views about disease. While I certainly wouldn't recommend it as a basis to learn about any one disease, it makes a good jumping off point for many of the diseases that are covered and it's a good reference for anyone trying to get a feel for the historical impact of disease generally.