Dark Money: The Hidden History of the Billionaires Behind the Rise of the Radical Right by Jane Mayer Doubleday, 449 pp., $29.95

In 2011, a blogger impersonating billionaire David Koch got through the switchboard at the Wisconsin State Capitol and was connected to Governor Scott Walker, who took time out from battling with the union protesters besieging Madison to truckle before what he thought was the great man. The recording of their conversation is a hard-to-listen-to blend of obsequiousness and braggadocio; at one point the faux Koch urges Walker to “bring a baseball bat” to negotiations with the state’s lawmakers.

“I have one in my office; you’d be happy with that,” Walker says. “I got a Slugger with my name on it.”

“I tell you what, Scott: once you crush these bastards I’ll fly you out to Cali and really show you a good time,” “Koch” says.

“That would be outstanding,” the governor responds. “Thanks, thanks for all the support and helping us move the cause forward, and we appreciate it. We’re, uh, we’re doing the just and right thing for the right reasons, and it’s all about getting our freedoms back.”

And then he adds, “Thanks a million!”

Walker was understating the case by at least three orders of magnitude. Jane Mayer’s remarkable new book makes it abundantly clear that the Kochs, and the closely connected group of billionaires they’ve helped assemble, have spent thousands of times that much over the past few decades, and that in the process they’ve distorted American politics in devastating ways, impairing the chances that we’ll effectively respond to climate change, reducing voting rights in many states, paralyzing Congress, and radically ratcheting up inequality.

In this election cycle, for instance, the Kochs have publicly stated that they and their compatriots will spend $889 million, more than either the Republican or Democratic parties spent last time around. According to a recent analysis in Politico, their privatized political network is backed by a group of several hundred extremely rich fellow donors who often meet at off-the-record conclaves organized by the Kochs at desert resorts. It has at least 1,200 full-time staffers in 107 offices nationwide, or three and a half times as many as the Republican National Committee. They may be the most important unelected political figures in American history.

As a result, Jane Mayer’s Dark Money—a detailed accounting of their rise and rise—is absolutely necessary reading for anyone who wants to make sense of our politics. Lay aside the endless punditry about Donald’s belligerence or Hillary’s ambition; Mayer is telling the epic story of America in our time. It is a triumph of investigative reporting, perhaps not surprising for a journalist who has won most of the awards her profession has to offer. But she had to cut through the secrecy that these men have carefully cultivated, unraveling an endless list of front groups. And she had to do it despite real intimidation; apparently an arm of what some have called “the Kochtopus” hired private investigators to try to dig…