The saga of Edward J. Snowden, the man whose leaked documents revealed the Orwellian dimensions of the National Security Agency, reads like a le Carri novel crossed with something by Kafka — at least it does in Luke Harding’s new book, "The Snowden Files."

A 29-year-old NSA contractor, alarmed by the agency’s vast surveillance dragnet, starts secretly collecting hundreds of thousands of classified government documents from his employer and turns them over to journalists, revealing the agency’s colossal reach and indiscriminate vacuuming up of information about people’s phone calls, emails and contacts.

The revelations not only pull back a curtain on the secretive agency’s expanded workings since 9/11, but also unleash an urgent public debate. A debate about the balance between civil liberties and national security; about the scope and protocols of U.S. government surveillance; about the relationship between the NSA and giant Internet and phone companies; about web infrastructure and national sovereignty; and about the meaning of privacy in a world in which Big Brother or Uncle Sam could be listening. Snowden, in the meantime, has become a fugitive, holing up first in Hong Kong and then in Russia — the world’s most wanted man.

Last June, The Guardian newspaper broke the first NSA article based on documents provided by Snowden; it appeared under the byline of the columnist Glenn Greenwald, whom Snowden had reached out to (along with the documentary filmmaker Laura Poitras). Greenwald left the paper last fall to join a new journalistic enterprise, and this Snowden book (by another journalist at The Guardian, Harding) seems timed, with its release this week, to get out ahead of a book by Greenwald scheduled for April publication.

Since Snowden went public days after the first article appeared in The Guardian, he has become a controversial figure, regarded by some as a hero, by others as a traitor. In "The Snowden Files" he emerges in a decidedly sympathetic light, as a protagonist who goes from unassuming geek to world-shaking whistle-blower. But Harding tends to depict his colleagues — reporters and editors at The Guardian who worked on the Snowden articles — as the real heroes.

Harding worked on several Snowden-driven articles for The Guardian about Government Communications Headquarters (known as GCHQ, Britain’s counterpart to the NSA), but was not part of the team that broke the first Snowden-NSA stories for the paper. His book, which lacks endnotes, breaks little new ground. It relies heavily on The Guardian’s reporting, as well as work from other sources, including The Washington Post (which also gained early access to Snowden through the reporter Barton Gellman), The (with which The Guardian has shared some of Snowden’s documents), books by the longtime NSA chronicler James Bamford, and various Snowden interviews and profiles in magazines and on the web.

Harding has spun all this material into a fast-paced, almost novelistic narrative that is part bildungsroman and part cinematic thriller, intercut with more Orwellian chapters about operations (with "Man From U.N.C.L.E."-like names including PRISM, TEMPORA, STELLAR WIND, MUSCULAR, BULLRUN, EDGEHILL) run by the NSA or GCHQ.

The portrait he creates of Snowden is a familiar one — a geek and gamer most at home online, who never graduated from high school but whose "exceptional IT skills" landed him a job with the CIA and later as an NSA contractor.

To flesh out a portrait of Snowden in his earlier years, Harding has drawn heavily on postings that appeared on the Ars Technica website in the first decade of this century under the username TheTrueHOOHA, even though it has not been positively confirmed that Snowden and TheTrueHOOHA are one and the same. Harding chooses to focus on postings that suggest TheTrueHOOHA was a conservative and libertarian — supportive of Ron Paul, impressed with John McCain and skeptical of Hillary Rodham Clinton — and at one point, in Harding’s words, was opposed to "government officials who leaked classified information to newspapers."

During a stint with the CIA, Harding writes, Snowden appears to have grown increasingly disillusioned with the tactics of the U.S. government. He joined the NSA as a contract employee in 2009; over the next years he said he discovered how far-reaching the NSA’s surveillance activities were — "they are intent on making every conversation and every form of behavior in the world known to them." He also became skeptical of congressional oversight of the agency.

Harding provides some bright digital snapshots of Snowden’s time in Hawaii, where he worked as an NSA contractor. He describes Snowden’s seemingly idyllic life on Oahu, with his girlfriend, a dancer and photographer named Lindsay Mills. Some of their friends teasingly likened Snowden to the vampire character Edward Cullen in the "Twilight" series because of his pale, solemn appearance, Harding reports. "E," as Mills reportedly called him, occasionally made an appearance in her photos online, Harding writes, but his face was routinely concealed.

Tension builds as Snowden settles on a plan — to leak top-secret stolen documents to journalists interested in civil liberties — that, Harding writes portentously, would "almost certainly" result in his "incarceration for a very long time and possibly for the rest of his life." And there is more suspense as Snowden engineers a high-risk rendezvous with Greenwald, Poitras and The Guardian’s veteran Washington correspondent Ewen MacAskill in a Hong Kong hotel room. There, the journalists vet their source, and Snowden begins to talk them through the trove of incredibly complex and technical NSA material — all while anxiously fearing a knock at the door.

Harding gives us a spy-novel-like sense of the tradecraft that Snowden and the journalists used, from encryption to old-school huggermugger meetings, but some mysterious gaps in the Hong Kong-to-Moscow story line remain. Of the period in Hong Kong after Snowden left that hotel, Harding writes vaguely that Snowden "went underground" with the help of a "mystery guardian angel" — "a well-connected Hong Kong resident" — who seems to have found him a place to stay with a friend. At one point, he writes, Poitras called MacAskill with the alarming news that Snowden had sent a message saying he was in danger. Hours later, a lawyer phoned back to say Snowden was OK. "The details were hazy," Harding writes, "but it appeared Snowden had survived a close call."

As for Snowden’s ability to protect his information while living in Moscow, Harding writes: "Snowden was extremely good at digital self-defense. When he was employed by the CIA and NSA, one of his jobs was to teach U.S. national security officials and CIA employees how to protect their data in high-threat digital environments." Paradoxically, he adds, Snowden now "found himself in precisely the kind of hostile environment he had lectured on, surrounded by agents from a foreign intelligence agency."

After The Guardian published its first scoops, there was a surreal scene in which, Harding reports, two men from GCHQ, "Ian" and "Chris" — called "the hobbits" by staff members at The Guardian — arrived at the newspaper’s London office to oversee the destruction of Snowden data, directing the demolition of computer parts with power tools and a data-erasing device. According to a November 2013 article by The Guardian’s editor, Alan Rusbridger, in The New York Review of Books, British government officials insisted on this destruction, despite explanations from The Guardian that such efforts were fruitless because copies of the Snowden material by then existed in other countries.

Harding — the author with David Leigh of "WikiLeaks: Inside Julian Assange’s War on Secrecy" — spends considerable space in these pages chronicling goings-on within The Guardian’s offices in London and New York, and explains the legal difficulties British journalists face without the sort of protections provided by the U.S. Constitution. Unfortunately, such discussions of the trans-Atlantic differences in journalism occasionally devolve into parochial and dubious boasts of British superiority, with Harding going so far as to assert that U.S. newspapers "pursue leads at a leisurely, even gentlemanly pace," and that the U.S. news media generally act "deferential towards the president."

Portions of "The Snowden Files" seem particularly aimed at a British audience, focusing at length on the surveillance activities of the GCHQ and its eager-to-please relationship with its wealthy U.S. counterpart. But the book still gives readers who have not been following the Snowden story closely a succinct overview of the momentous events of the past year.

And if it leans toward dramatizing everything in thrillerlike terms, the book also manages to leave readers with an acute understanding of the serious issues involved: the NSA’s surveillance activities and voluminous collection of data, and the consequences that this sifting of bigger and bigger haystacks for tiny needles has had on the public and its right to privacy.

© 2014 The New York Times Company