I had to read this for one of my classes at university. It's about the cholera outbreak in London when they figured out how cholera was spread, and the 2 guys who figured it out. It was very dryly written, but many aspects of the book were fascinating. The problem was that Johnson would go off topic a lot and go on and on about how stupid the miasma theory (that disease is spread through bad air rather than, in this case, water) and how he couldn't understand how the great minds of the time like Florence Nightingale and Charles Dickens could believe it. And then the last part was his thoughts on urbanization in modern times, which was also pretty filled with tangents.