Stieg Larsson's partner Eva Gabrielsson plans to finish the fourth novel he left uncompleted on his death. According to early details culled from Gabrielsson's memoir of her life with Larsson, Millennium, Stieg and Me, which is set for publication in France and Scandinavia next week, Larsson had written 200 pages of a fourth novel in his internationally successful Millennium series before he died. Gabrielsson wants to complete it because, she says, "Stieg and I often wrote together".

Larsson's partner has refused to reveal details of the partially completed novel's plot, but promised that its charismatic but damaged protagonist Lisbeth Salander "little by little frees herself from her ghosts and her enemies". And, she said, she will only finish the book when she gets undisputed rights to Larsson's work from his family, who inherited the author's assets when he died intestate.

Swedish journalist Larsson died in 2004, aged 50, before any of his three completed Millennium titles – The Girl with the Dragon Tattoo, The Girl Who Played with Fire and The Girl Who Kicked the Hornet's Nest – were published. The crime novels featuring crusading journalist Blomkvist and punk hacker Salander have gone on to become a publishing phenomenon, with approaching 50m copies sold worldwide. But Gabrielsson is involved in an extended dispute with the author's father and brother over the proceeds from the books because the couple remained unmarried, despite being together for more than 30 years, leaving her with no rights to his assets under Swedish law. Reports of an uncompleted fourth novel, left on Larsson's computer and in Gabrielsson's hands, have been circulating for several months.

Millennium, Stieg and Me chronicles how the couple met and their struggles together at Expo, the anti-fascist publication Larsson founded in 1995. Larsson and his staff "moved around constantly to escape the Nazis who were harassing them", Gabrielsson writes.

And in a criticism of the Larsson family's handling of the estate, she sounds off about the Millennium "industry and brand", saying: "I don't want to see coffee mugs and other 'Millennium' merchandise; I want to see the 'real' Stieg respected." She has previously complained about the parasitic industry that has grown up around Larsson, describing the "mythology" as unbearable.

Given Gabrielsson's concerns over how Larsson's legacy is handled, she is unlikely to be impressed with news emerging of the forthcoming Hollywood version of The Girl with the Dragon Tattoo, set to star Daniel Craig as Blomkvist and Rooney Mara as Salander. The latest issue of W Magazine reports that the new film departs "rather dramatically" from the book, including alterations to its two main protagonists (Blomkvist less promiscuous; Salander even more aggressive) and a "completely changed" ending, which the magazine does not reveal but votes "more interesting" than the original. The new film, which has already attracted controversy for recasting the role of Salander, taken in the Swedish film version by Noomi Rapace, with an American actress, is expected to be released late this year.