To call David Lagercrantz a Lisbeth Salander “fan” would be an understatement.

“I’ve been obsessed, really,” Lagercrantz says of Stieg Larsson’s famous punk superhacker. “The genius of her is so fascinating, of course, but also the mythology: the girl against the world, the girl the world treated so exceptionally badly but she refused to be a victim....She’s a new crusader, of sorts, and I think she’s absolutely fantastic.”

Lagercrantz is the Swedish journalist and bestselling author (I am Zlatan Ibrahimović, 2011) chosen by Larsson’s estate to extend the Millennium series, the global literary phenomenon launched by The Girl with the Dragon Tattoo.

Ahead of the U.S. publication on Sept. 1 of The Girl in the Spider’s Web: A Lisbeth Salander Novel, Lagercrantz met with Kirkus in the sleek basement of a Midtown Manhattan boutique hotel. That day, select American journalists were given 15 minutes to read a brief excerpt, which was collected at the end of each 30-minute interview. No review galleys were made available until shortly before publication.

It’s an unusual level of security, reserved only for the most fiercely anticipated literary launches. For Lagercrantz, the pressure to meet readers’ and publishers’ expectations is correspondingly immense.

“I’ve been scared to death to write this and not to live up to [Larsson’s] quality,” he says. “But I believe in being scared sometimes. It gets your concentration up to experience danger. You see the details more, then you get more confident. I think the pressure drove me to write better and that [one] should take risks. If you don’t take risks, you will be disappointed at the end of your life.”

The Lisbeth Salander of Spider’s Web is brilliant, ambitious, and a risk-taker. Early on, she performs the seemingly impossible feat of hacking the American NSA—and sends a cheeky message to intelligence head Edwin “Ed the Ned” Needham as proof:

“Those who spy on the people end up themselves being spied on by the people. There’s a fundamental democratic logic to it,” Lagercrantz writes.

While embarrassing the NSA delights her fellow hackers, it’s not her main objective: Salander is pursuing the Spider Society, a cyber-Mafia with questionable ties to American technology corporation Solifon. How this association connects to the murder of Artificial Intelligence pioneer Frans Balder—witnessed only by his nonverbal, autistic son—and investigative journalist Mikael Blomkvist is a puzzle to unravel, at her own peril.

“[A]ll of a sudden Salander shouted to Ahmed to stop. She jumped out of the moving car, just as the man across the street raised his right hand and aimed a pistol with a telescopic sight at the door as it slid open,” he writes.

Action-packed? Yes. But for Lagercrantz, it’s less about body count than weaving a tantalizing web.

“I’m not that fond of too much violence—I’m more fond of the riddle of the intellectual mystery,” Lagercrantz says. “The genius of Stieg Larsson is his intrigue; his plots are so complex. It’s not just one murder that they had to solve, it’s so many threads coming together, and that was really a challenge, to be aware of that legacy.”

Many of the Millennium trilogy threads permeating Spider’s Web lead back to Larsson’s most complex character.

“I understood that I had to go back,” Lagercrantz says. “The real start, the creation of Lisbeth Salander is her horrible childhood, and there are still so many questions to answer back there as to what really happened. For example, why is she such a good hacker? We will see.”

Megan Labrise writes features for Kirkus Reviews.