The Ghost Map by Steven Johnson

In 1854, London found itself in the grip of a cholera epidemic. The prevailing "scientific" theory was that the pestilence was carried by the foul air arising from the open sewers running through Victorian London - a miasma. Two people, John Snow, a doctor obsessed with sanitary reform, and Rev. Henry Whitehead, a local minister, are more responsible than any others for identifying the water source carrying the disease. Johnson makes the argument that, in addition, they also set the stage for proper understanding of epidemiology and made possible the conditions that allowed for urban development. Although a bit of a stretch, his argument is well researched and convincing.