The text contains the substance of all of Snow's articles published since the first edition of 1849, "together with much new matter" (Preface, p. iii), making this essentially a new work.

Within the work Snow provides detailed historical and statistical evidence for his conviction that cholera is a contagious disease that attacks the alimentary canal and is communicated primarily through contaminated water. His examination of the patterns of infection of the London epidemics, correlated with a survey of the water sources in each neighbourhood, was particularly conclusive.

"In the great London epidemic of 1854, Snow's genius as an epidemiologist and statistician reached fruition. By meticulous survey he established [in the present work] that the areas supplied by water from the Southwark and Vauxhall Water Company, obtained from the fecal-contaminated Thames, were infected nine times more fatally than the areas supplied by the Lambeth Company, which supplied water from an upstream source. Even more dramatic was the affair of the Broad Street pump [first described here], which he showed by careful plotting to be in the centre of a cholera outbreak in his own parish of Soho. Within a few hundred yards of this pump, some five hundred fatal cases occurred in ten days. Snow found that a sewer pipe passed within a few feet of the well, and his belief that contaminated water was the source of infection was vindicated when he persuaded the parish councillors to remove the pump handle" (DSB), resulting in a dramatic drop in the number of cholera cases. Thirty years before Koch's discovery of the cholera vibrio, Snow reasoned that the disease was propagated by a living organism, and recommended hygienic precautions such as boiling water of suspicious origin, washing the hands frequently, and decontaminating soiled linen. "Snow's writings and practice were a very considerable influence upon the great sanitary reformers such as Sir John Simon and Sir Edwin Chadwick in the later part of the century" (DSB).

The first map in the work focuses on Broad Street and the surrounding area: public water pumps are marked together with stacked bars symbolising each cholera victim, which graphically illustrates the centre of the cholera outbreak near the Broad Street pump; it is the first use of a spot map in epidemiology.

Rare we are only aware of one other example to come up for sale in the last 40 years: the Haskell F. Norman copy, Christie's, 1998, and 2010.