By a generous estimate, evangelical Christians are as much as one third of the U.S. population. In fact, they are the only Christian demographic that has shown exuberant growth in recent decades—a period during which church attendance overall has been steadily eroding. A significant part of this growth has taken place in the nondenominational or loosely affiliated “megachurches,” though not all of these are evangelical. Some, strictly speaking, are fundamentalist, though the distinction between the two is not always clear to outsiders. In Sacred Subdivisions Justin Wilford focuses exclusively on what he calls “post-denominational evangelicalism,” especially as it manifests itself in the megachurch phenomenon. Wilford is well aware that a number of books and hundreds of articles have analyzed the evangelical success story, but he is persuaded that one important aspect of it has been either ignored or given at best superficial treatment. In short, as his subtitle suggests, Wilford argues that the growth of megachurches like Saddleback Church in Orange County, California, must be understood not only sociologically but geographically. Those who adopt the currently fashionable “religious market approach” to explain the rise of the megachurches often claim that their success is simply a matter of effective marketing of a new...