"The three copies we had in stock have sold, and I'm going through the draft orders now," said Dave Cameron, owner of Christchurch bookseller Scorpio Books.
"I wondered when we got to 1984 if it would stop selling, but it's timeless and continues to live on."
A spokesman for Paper Plus said their records showed not a single copy of 1984 had been sold in the last month.
The book, originally published in 1949, portrays a world with a totalitarian government that constantly tracks the thoughts and movements of its citizens.
Snowden's leaks highlighting the extent of NSA's prying has been prophetic for some people.
"Throwing out such a broad net of surveillance is exactly the kind of threat Orwell feared," Orwell biographer Michael Shelden told National Public Radio.
President Barack Obama referenced the novel last week when defending the NSA programme, saying, "In the abstract, you can complain about Big Brother and how this is a potential program run amok, but when you actually look at the details, then I think we've struck the right balance."
Penguin, the book's publisher, says there's a clear link between the NSA news and the sales spike.
"It is exciting that Orwell's classic is being discovered by a new readership and rediscovered by readers, but not surprising," Penguin's Liz Keenan told TODAY.com.
"Of course the themes and political and social issues explored in the book feel even more relevant. And the current news cycle, prophetic."
Author and investigative journalist Nicky Hager, who has written about New Zealand's spy agency, the Government Communications Security Bureau, was unsure whether the NSA leaks would boost sales of his work.
But he was glad the revelations had prompted people to think about their privacy and many were turning to read 1984.
"Orwell was hypothesising a horror story according to 1948 technology. But online tools used to spy on people's lives? It's beyond anything he could ever have imagined," Hager said.
He praised Snowden for his "principled, brave" move, which he said has "completely changed the world".
But he worries about what will happen to Snowden now.
"I'd say he's a tremendously vulnerable person. As he said himself, he kind of expects trouble, and I think he'll get it."