Epstein proves none of this. “How America Lost Its Secrets” is an impressively fluffy and golden-brown wobbly soufflé of speculation, full of anonymous sourcing and suppositional language like “it seems plausible to believe” or “it doesn’t take a great stretch of the imagination to conclude.” Epstein’s first book, “Inquest,” published more than 50 years ago, featured another mysterious young man who spent time in Moscow, Lee Harvey Oswald. This book has a greatest-hits feeling, because it touches on several of Epstein’s long-running preoccupations: Russia; the movie and media businesses; the gullibility of liberals; and, especially, the world of penetration, exfiltration, false flags and other aspects of counterintelligence. The spirit of James Jesus Angleton, the C.I.A.’s mole-obsessed counterintelligence chief during the peak years of the Cold War and evidently a mentor to Epstein (he’s mentioned several times), hovers over these pages.

Sometimes it seems as if Epstein so much enjoys exploring the twists and turns in Snowden’s story — his encounter with Snowden’s mysterious lawyer in Moscow, Anatoly Kucherena, is especially memorable — that he doesn’t have an overwhelming need to settle the questions he raises. The sentence from The Wall Street Journal quoted above appears almost verbatim in the book, but it’s immediately followed by this: “These severe accusations generated much heat but little light. They were not accompanied by any evidence showing that Snowden had acted in concert with any foreign power in stealing the files or, for that matter, that he was not acting out of his own personal convictions, no matter how misguided they might have been.” But then Epstein spends many more pages considering, and not dismissing, the very same severe accusations, and ends by saying that “Snowden’s theft of state secrets . . . had evolved, deliberately or not, but necessarily, into a mission of disclosing key national secrets to a foreign power.”

This is Epstein’s primary conclusion: Even if the American public was a partial beneficiary of Snowden’s revelations, the main beneficiary was Russia, which to his mind couldn’t possibly have failed to take possession of all the material Snowden took from the N.S.A. Whatever caveats he uses and whatever hard evidence he hasn’t found, Epstein clearly wants to leave readers with the impression that Snowden remains in Russia as a result of a deal exchanging his information for its protection. He repeatedly hints that he has reason to be more certain about his conclusion than he’s able to say in print; for one tantalizing example, among the names on a list of people he thanks for their “insights, erudition and criticisms” after reading part of the manuscript is the outgoing secretary of defense, Ash Carter.

Snowden, Julian Assange of WikiLeaks, and their immediate circle of allies come from a radically libertarian hacker culture that, most of the time, doesn’t believe there should be an N.S.A. at all, whether or not it remains within the confines of its legal charter. Epstein, conversely, is a strong supporter of the agency’s official mission of “communication intercepts,” which he sees as an essential element in the United States’ ability to participate in “the game of nations.” To him one of the lessons of the Snowden case is that the agency’s reliance on private contractors like Snowden instead of career employees has made it dangerously vulnerable to security breaches.

It’s an irony of the years since the Reagan revolution that one political strain in the United States, suspicion of big government, has led to spending and staffing limits that have pushed the N.S.A. into the low-security private marketplace to perform its ever-expanding mission. (The contractor that employed Snowden had been acquired by a private equity firm that was pressuring it to cut costs, and elaborate background checks are expensive.) That conflicts with another strain of modern conservatism, support for a vast national-security apparatus. Whatever his motive, Snowden found a way to arbitrage that contradiction.

The age of the internet, Vladimir Putin, Snowden and WikiLeaks has generated its own particular form of disruption around how we think about the revelation of government secrets. Traditional spies seem far less important these days, because unclubbable, technically adept people can do that kind of work far more effectively. The press, at least for now, has assumed a larger role in the ecosystem of revelation, because hackers prefer finding partners in the mainstream media to simply releasing information on their own. But this new set of arrangements makes journalists look more like conduits and contextualizers, and less like originators of information. Reporters aren’t supposed to be hackers themselves (see the News of the World scandals in London five years ago), but they’re not capable of resisting juicy information that others have hacked, no matter how unsavory the purpose (see the ubiquitous coverage of John Podesta’s Russian-hacked private emails during the fall campaign).

Journalists are quite comfortable with the idea of the news media uncovering government secrets that should not have been secret in the first place. This may be a role whose run is coming to an end. Information is too copious and flows too freely, and there are too many players in the revelation game — political activists, foreign governments, tricksters, self-publishers — for journalists to function as the arbiters of revelation. If there isn’t any longer going to be one trustworthy group in society, the established press, that acts as a benign check on excessive government secrecy, the discussion of what should and shouldn’t be secret becomes a lot messier.

Epstein has long been annoyed with the idea of the press as the key actor in secrecy dramas, digging up what the public should know but not exposing everything willy-nilly. Way back in 1974, he published an article in Commentary called “Did the Press Uncover Watergate?” (His answer: no.) This time around, his concern seems to be half with the celebratory closed loop between Snowden and the journalists who covered him, and half with the causes and consequences of a major security breach at the N.S.A. The heart of the matter is the second of these concerns, not the first. In the Snowden affair, the press didn’t decide what stayed secret, and neither did Congress, the White House or the N.S.A. Snowden did.