Mostly, an academic jots down observations of people goofing around in cities' public spaces. Pedestrians waggle their arms. Buskers and street crazies accost passers-by. Bicyclists ride in perhaps-surprising places. It's a strange thing to write down; this book seems to be a reaction to city planners who think in terms of function. When laying out a plaza, serious-minded planners are unlikely to consider the opinions of grind-happy skateboarders (except, perhaps, in hopes of thwarting them). But perhaps if they want those public spaces to be used by the public, they should consider how folks might goof around in those spaces. (Is this a real controversy? I don't know; I don't read much about city planning.)