The Swedish publisher of the best-selling The Girl With the Dragon Tattoo trilogy said Tuesday it has hired an author to write a sequel to the series by Stieg Larsson, who died in 2004.

Norstedts said it signed a contract with David Lagercrantz, the author of I am Zlatan, a biography of Zlatan Ibrahimovic, the captain of Sweden's soccer team, to write a new novel about journalist Mikael Blomqvist and hacker Lisbeth Salander that is scheduled to be published in August 2015.

Larsson's trilogy about a darker side of Sweden, including murder mysteries, sex trafficking scandals and a secret government unit, has been a huge international success, with more than 75 million books sold in 50 countries.

The head of publishing at Norstedts, Eva Gedin, told The Associated Press the book will be an original work that includes nothing from the fourth book in the series that Larsson began writing but hadn't finished when he died at age 50.

"Obviously it will build on the previous books," she said.

"Blomqvist and Salander will be included and many of the other characters."

Decision taken after long discussions

Gedin said the decision to continue the series had been taken after careful considerations and long discussions with Larsson's father and brother, Erland and Joakim Larsson, who own the rights to his work.

Lagercrantz said he was really skeptical about the idea of writing a fourth book in the series at first, but that changed when he reread Larsson's novels.

"I increasingly felt that these characters, Blomqvist and Salander, deserved a longer life," he told The Associated Press.

He wouldn't reveal anything about the plot, but said: "In the times we live in, where we are monitored by American authorities like the NSA, a hacker like Lisbeth Salander is needed."

"We will meet her again in all her complex splendor," he said.

Larsson's longtime partner, Eva Gabrielsson, who has been in a legal dispute with Erland and Joakim over the rights to the trilogy, told daily newspaper Aftonbladet she finds it "tasteless" to try to make more money out of something that is already so successful.

"I guess I think it's greedy. It's already a multi-million dollar industry," she was quoted as saying.

Gabrielsson and Larsson were a couple for more than 30 years, but they never married. Larsson didn't leave a will, so only his brother and father inherited the rights to his works.

Since Larsson's death the whereabouts of his unfinished fourth manuscript have been clouded in mystery. Gabrielsson first said she had a laptop containing the manuscript, but later said she does not have it and does not want to see any other book in the Millennium series published

His bestselling series inspired a hit Swedish film trilogy starring Michael Nyqvist and Noomi Rapace. A subsequent and acclaimed English-language movie adaptation of the first book starred Daniel Craig and Rooney Mara.