This book critiques suburban and urban forms of the late 20th century and argues for human-scale architecture and urban planning.
Kunstler recounts the settlement patterns through the history of the United States and how these seem tied to American's attachment to mobility, individual freedom, private space, and ultimately suburban sprawl. He criticizes the urban policies that decimated Detroit and praises the people-oriented plans of Portland, Oregon. He examines LA's (and suburban) non-sustainability.
A big strength of this book is that Kunstler argues for human-scale urban planning and architecture to be legal (e.g., make it legal for housing above stores, lot sizes to be small, retail stores to be near housing, smaller streets to calm traffic). These concepts are at the heart of New Urbanism (see Suburban Nation, for example).
Kunstler ideal urban form is one in which people can live in "a web of practical interrelationships between neighbors who understand their mutual dependency and honor it by competently caring for their work, their town, their offspring, and each other" (p. 241).
Kunstler's argument seems to imply that private space is somehow anti-urban. I find this difficult to accept (having achieved private space in an urban environment myself). Moreover, I think suburbanites who would consider a move to the city may be put off by the idea of needing to participate in "a web" of interrelationships with their neighbors.
Kunstler's argument on the unsustainability of suburbs may come to be seen as prescient, but this book was published more than eight years before the 21st century's start, and the suburbs by the century's turn had grown out to the ex-burbs, and are still growing and growing (However, see Kunstler's book, The Long Emergency).