Rats centres around a single New York alley way, called Edens Alley, over the course of one year. In the book, Robert Sullivan spends that year watching and getting to know the rats of Edens Alley and learns a lot about rats, humans and New York City.

Why does Sullivan set out on his year of ratting? He gives a number of answers:  because of their proximity to humans and the parallels between the story of rats and the story of humans in America; because they have typically been excluded from the pantheon of natural wonders; because of, as Sullivan puts it, the propensity that I share with rats toward areas where no cruise ships go, areas that have been deemed unenjoyable, aesthetically bankrupt, gross or vile.