“How will we know it’s him?” Glenn Greenwald asks Laura Poitras, a documentary filmmaker, early in “No Place to Hide,” his memoir of the Edward Snowden revelations. “He’ll be carrying a Rubik’s Cube,” she replies. And, indeed, when they first see Snowden, in a Hong Kong hotel, the cube is in his hands. (“Unsolved,” Greenwald notes.) After talking to him for hours, neither Greenwald nor Poitras has any doubt about who or what Snowden is—someone who just wants the public to know about the excesses of government surveillance.

What is striking, though, is how much of Greenwald’s book is about mistaken identities. He acknowledges some of his own bad guesses about who people are, at times to comic effect. Months before the rendezvous in Hong Kong, Greenwald had received e-mails from someone using the name Cincinnatus, who had urged him to install P.G.P. encryption software so that he could send him information—something that Greenwald had never found the time to figure out, until Poitras brought him into the N.S.A. story. Deep into his sessions with Snowden in Hong Kong, he suddenly remembers Cincinnatus: “I thought perhaps he, too, had an important story to give me”:

“Hey: good news,” I wrote to him. “I know it took me a while, but I’m finally using PGP email. So I’m ready to talk if you’re still interested.” I hit “send.” Soon after I arrived in his room, Snowden said, with more than a small trace of mockery, “By the way, that Cincinnatus you just emailed, that’s me.”

He didn’t realize that Snowden was someone he’d already met online; he was shocked to find, when they met in person, that he was in his twenties, not, as in the profile Greenwald had drawn in his head, in his sixties. “My mind began racing to consider the possibilities…. Maybe, I thought, this was the source’s son, or assistant, or lover, who was now going to take us to the source himself.” (Snowden was young enough to tell Greenwald that his ethical development had been influenced by video games and to joke, “I call the bottom bunk at Gitmo.”)

Greenwald was also mistaken in his early assessments of some of his colleagues, particularly at the Guardian. When Janine Gibson, the editor of the Guardian’s American operation, insists on one of her reporters, Ewen MacAskill, travelling with Greenwald and Poitras to Hong Kong, they are, to put it mildly, grumpy and distrustful. Meeting him at the gate for their flight, “Laura and I were cordial but cold, wanting him to feel excluded…. We treated him like extra baggage with which we had been saddled.” They described him to Snowden as the “babysitter.” It was, Greenwald realized, “unfair”—something brought home to him after MacAskill meets Snowden, questions him for two hours, and then tells Greenwald he’s persuaded that he’s real, and will urge the Guardian to publish:

We realized that our suspicions had been entirely unfounded: lurking under the surface of Ewen’s mild-mannered, avuncular exterior was a fearless reporter eager to pursue this story in exactly the way we all thought necessary.

To Greenwald’s credit, he is open about how turned-around he was—for him, it appears to be of a piece with the wonder and the value of the story, the casting aside of notions about what a whistleblower looks like, who is willing to be brave, and, most importantly, what the N.S.A. is willing to do or ignore. This is good reading, although one gets that sense that, with some of the characters, Greenwald may be stuck at an earlier, more rigid stage. (He disparages the motives of some of the others involved in publishing the papers—at the Washington Post, with whom the Guardian shared a Pulitzer, and the Times—in a way that can feel reflexive.)

One of his biggest arguments in the book, though, has to do with the way that his own identity has been mistaken, or altered beyond recognition. After the story breaks, other journalists ask whether he counts as one of them. (Gibson also gets told by the Obama Administration that she is not acting like a “serious journalist.”) He is asked if he is really a reporter, or some sort of “activist.”

What are the definitions here? Greenwald had been writing for years for recognized media outlets; he got a lead, reported it out, met and vetted his source, consulted with editors, and published stories, which included comment from the government, on a matter of true public interest. How could opinions be disqualifying, when whole media outlets have been built around philosophies, muckraking campaigns, and points of view? Nor does publishing classified papers, per se, mean that you stop being a journalist; such documents have, often enough, been central to the sort of stories that journalists cite when explaining why the profession matters. Greenwald notes that he was working for a newspaper that was more than a century old; that wouldn’t matter—new media outlets deserve protection, too—except as a measure of how off it was to argue that he was some high-tech oddity for whom the old categories were inadequate. (His clumsiness with the encryption program would suggest otherwise.) Is it that Greenwald and Poitras make things difficult for the government? That used to be the idea of the enterprise. This is a journalist’s story, written by a someone who clearly is one. As Greenwald notes, the argument that he is not a journalist isn’t just a matter of snobbery; it has legal consequences, and is a step from calling the important work he and his colleagues have done espionage. Any definition that excluded Greenwald would, I think, leave reporters at publications like this one exposed, too.

Snowden’s identity presented different questions—he has, as he knew from the start, put himself in serious legal jeopardy. Greenwald writes that it was important to Snowden that he make his own name public, and to explain himself—before the government did it for him. That didn’t mean that he wanted to spend the rest of his life in jail. First, he has to get out of the hotel, where a crowd of reporters has gathered. “I’m in the process of taking steps to change my appearance,” he tells Greenwald on the phone. “I can make myself unrecognizable.”

Above: Glenn Greenwald, in Hong Kong, in 2013. Photograph by Vincent Yu/AP.