The book "Designing the Modern City: Urbanism Since 1850" by Eric Mumford explores how cities have evolved since the industrial revolution. Mumford discusses how urban environments have been shaped by key figures in design, leading to the creation of the field of "urbanism." The book covers the modernization of cities, including the development of mass transit systems, building regulations, and urban planning approaches. It also delves into the concepts of urban design groups like CIAM and Team 10, as well as efforts towards ecological urbanism. Overall, the book provides a comprehensive overview of the history of urban design and how designers have influenced the development of cities over time.