Ehrenhalt's thesis is that the post-war demographic shift is now seeing its inverse with young and affluent (largely white) people moving to the city while immigrants, minorities and poorer people are heading to the suburbs.
Despite this basic premise, the cities and neighborhoods Ehrenhalt visits are all facing unique challenges. There's New York City's Financial District that's seeing an unexpected conversion of office space to residential, but without the mom 'n pop shops deemed vital to a healthy community by famous urbanist Jane Jacobs. There's Phoenix and the suburbs of Denver, CO struggling to redefine themselves as "walkable, transit-oriented" in an era far removed from the post-war sprawl mentality they were born into. And there are places like Philadelphia ("Bostroit") that are thriving in the downtown core but remain crippled under a glut of abandoned buildings elsewhere.
It's clear that the urbanist revival of the past 15 years or so is still struggling to find its footing. Much of the development (in the suburbs especially) seems to capture the facade of city life, but not its heart. Reston Town Center in Virginia, West Hartford, CT's Blue Back Square and the rest of the new crop of polished suburban "downtown centers" seem more eager have people buy things than to foster civic engagement.
There are two factors that Ehrenhalt glosses over to the book's detriment. The first is the role that energy, climate change and resource scarcity play in the future of cities. He cops out by saying he's not an energy policy expert, a frustrating statement considering cities consume 75% of the world's energy and the enormous challenges they face in light of that.
And while race and inequality are part of his thesis, Ehrenhalt says that there's nothing much to be done about segregation by class, that it's "a fact of American life". In this way he brushes aside the idea that equality (or lack thereof) might be the most important factor determining the shape of our cities. Enrique Peñalosa, former mayor of Bogotá (it's difficult not to quote a Colombian mayor these days) puts it best: "A city needs to show as much respect for a person riding a $30 bicycle as it does for someone driving a $30,000 car." American cities just aren't there yet.