One of the overarching themes of the book is that worsening living conditions in many cities around the world are the result of a constant war waged on the poor by the rich. Davis argues this point through statistics and historic examples, which interpret the situation through a Marxist lens, concluding that the world’s richest minority is doing its best to retain and expand of wealth, forever widening the gap between rich and poor.

Davis points out that counterintuitively, slums are quite lucrative for landlords: “Overcrowded, poorly maintained slum dwellings, meanwhile, are often more profitable per square foot than other types of real-estate investment” (86). Slums become profitable in a number of ways: their sheer density, the lack of governmental regulation and safety oversight, and the fact that governments often reimburse owners for renting below market rates. All of this disincentivizes people with financial and political power from doing anything to improve slum living.

At the same time, the class conflict Davis describes erupts in other ways. Slum evictions or slum clearances force displaced residents to increasingly smaller areas as they cling to the proximity of work—making those areas all the more profitable as they become the only available cheap slum housing.