There are parts of the federal government that D.C. residents are generally aware of on a daily basis: the stressed-out Hill staffers who scuttle around, tossed in the Congressional tempest; the White House officials and their visitors who sweep through town, hidden in cavalcades of black SUVs; the bureaucratic beehive in Federal Center Southwest, busy crafting regulation.

But one of the biggest pieces of the federal presence has mushroomed over the last decade in ways you’d only notice indirectly. In the years following Sept. 11, 2001, the nation’s intelligence apparatus has grown into a thicket of new agencies, commands, task forces, and centers with overlapping responsibilities that can be depicted on an organization chart only very approximately. Most of that centers in and around Washington, with 17 million new square feet of office space either completed or under construction since the attacks.

Top Secret America is the extended version of a Washington Post series principally reported by Dana Priest and William Arkin, who burrowed as far into this shadowy new world as any pair of journalists ever has. Naturally, the work suffers from some of the flabbiness that often results when articles are packaged into a book. Priest spends too much time writing in conspiratorial tones about the parking garages and conference rooms where she met her often-nameless sources. And there’s something gimmicky in the treatment of this top-secret America as a unprecedented parallel world with its own rules and norms. We’re left wanting some historical perspective on how this incredible buildup compares to previous outbreaks of national paranoia.

The additional running room, however, allows the authors to more fully flesh out how the Byzantine security maze actually works, breaking down its components. In the process, they reveal a lot about how the D.C. economy works, too: what goes on in all that Crystal City office space (monitoring data and creating ever-better technology to do it), why your GPS goes on the fritz on I-95 between D.C. and Baltimore (thanks to the National Security Agency, which houses what the authors call the “Loneliest Starbucks in America”), and how the D.C. area got six out of the 10 wealthiest and best-educated counties in the nation (all those contractors make a crapload of money). Priest also has a sociologist’s eye for how these citizens interact with the world around them: The 854,000 people with national security clearances tend to contribute only economically, rather than civically and socially, to the communities they call home.

Finally, having taken off their Post hats, Priest and Arkin are freer to drive home their personal conclusions about this massive chunk of the government that’s been given everything it could ever want—by Democrats and Republicans alike. The authors’ arguments are compelling: that for all their determination to create a system where terrorists can’t slip through America’s fingers, the officials who are supposed to oversee and coordinate everything don’t have the authority to do so; that the volume of information generated about potential threats has just led intelligence officials to tune it out; that contractors have become more expensive than anyone had ever imagined. Meanwhile, a security regime run by people in their 50s and 60s failed to foresee the social media–driven revolutions in the Middle East.

All of that’s not great news for the Washington region, which benefited disproportionately from the gushing cash spigot that created this top-secret climate, and will suffer when it’s ultimately tightened. But from a global perspective, take it from Arkin and Priest when they say that the rest of the country doesn’t have much to show for it.