Social science has spent its energy on formal institutions, Laguerre observes, inheriting from the Enlightenment the conviction that societies improve by being rationally ordered. He proposes reversing the procedure: study the American city from the standpoint of informality and let the formal system be understood from there.

Informal practices in his account are neither marginal nor residual but permanent and structuring, at once peripheral and central to how a city works. Some predate Western formality and survived its imposition through colonization; others exist simply because no formal apparatus can regulate everything.

His material comes largely from the San Francisco Bay Area and Oakland. He shows space being informalized from the supply side, by traders spilling out of premises, and from the demand side, by the customer who turns a street into a mechanic's shop, and he follows firms adopting flexible workplace arrangements until home and office, formal and informal work, blur into each other.