"That Which Does Not kill" was completed in November by David Lagercrantz who is best known for co-authoring Swedish football star Zlatan Ibrahimovic's autobiography. He stands in for Larsson, who died of a heart attack in 2004 aged 50.
The book will continue the story of the troubled but resourceful heroine Lisbeth Salander first made famous in Larsson's "The Girl with the Dragon Tattoo".
But the author remained tight-lipped about the meaning of the title or what direction the action-packed political thriller – 500 pages long in Swedish – will take.
"What I wanted to make use of in the book was the vast mythology that Stieg Larsson left behind, the world he created," Lagercrantz told Swedish newspaper Dagens Nyheter on Tuesday, adding that he remained loyal to Larsson's writing style which weaved criticism of social and political issues with criminal intrigue.
"Lisbeth Salander's not just any superhero. She's not only great because of her talents but also because of her context and background."
At the time of his death Stieg Larsson reportedly had plans to write at least another seven novels.
His publishers Nordstedts have compared the planned release on August 27th of the book in many of the 35 countries which have signed a publishing deal, to the global splash made by Dan Brown's "Da Vinci Code" in 2003.
Nordstedts said the first three books in the Lisbeth Salander series have sold in the region of 80 million copies worldwide since the first book, "The Girl with the Dragon Tattoo" went on sale in 2005.