My role in Stieg Larsson's success, by partner who was left with nothing

If it followed the pattern of Stieg Larsson's Millennium Trilogy, Eva Gabrielsson's book might be called "The girl who was cheated of millions". Alternatively, it might even be called "The girl who co-wrote the biggest literary phenomenon of the 21st century".

Eva Gabrielsson, Larsson's long-time partner, does not exactly claim to be the co-author of the three Swedish thrillers written just before his death in 2004. At times in her book, published so far in Sweden and France, she specifically rejects suggestions she was the ghost author of the books, which have sold 40 million copies around the world. Elsewhere, she makes teasing reference to their artistic union.

"It is one of life's little ironies," she writes, "that some people say that I made no contribution at all and some people say that I wrote them from end to end. I can only say that, just as [Stieg and I] shared our own personal language, we also often wrote together."

Ms Gabrielsson, 56, also makes several statements on the whereabouts of a fourth, potential gold-mine of a book which may, or may not, be in her possession. She also lashes out at what she sees as the commercialisation of her late partner's name by his relatives, writing: "The way things are going, his name could end up on a bottle of beer, a coffee packet or a car."

But Ms Gabrielsson insists her ferocious and much-publicised legal battle with Larsson's father and brother is not about money but to prevent the "Larsson industry" from distorting his work. In particular, she fears that the terms of the deals struck with publishers and film-makers will allow the creation of money-spinning "Larsson" books and movies which have nothing to do with his real work or ideas.

On balance, it is fair to say Ms Gabrielsson does not finally claim to be the "real author" of the trilogy. What she does claim, and largely prove, is that "our experiences side-by-side over 32 years were the data base for these books. Our struggles, our commitments, our travels, our passions, our fears... These books are the jigsaw puzzle of our lives".

On the rumoured fourth book – the subject of intense speculation and another legal battle – Ms Gabrielsson teases her readers like any publisher's blurb. She says that just over 200 pages were written by Larsson before his death, aged 50, in November 2004. She says the work exists only in a laptop computer, which she may or may not have.

At any rate, she knows where the computer is and could finish the book – "something I would be quite able to do". One of the reasons why many people in Sweden have cast doubt on Larsson's authorship of the trilogy is that he had a reputation as a good and passionate journalist, but a poor writer. Ms Gabrielsson's book – often muddled and badly written – might also be taken as proof she could not have been the real writer of the Millennium Trilogy.

In her book, Millénium, Stieg et moi, Ms Gabrielsson does put Larsson's often chaotic life into context. Her partner, she says, was a feminist, a hopeless businessman, a journalist who could not hold down a staff job, and a passionate fighter and investigator for social causes and against the Far Right. She describes how the manuscript for the first book was sent to the Swedish publisher Piratförlaget in autumn 2003 – and never opened. All three volumes were eventually accepted by another Swedish publisher for €64,000. Their earnings over the last six years run into hundreds of millions. The three works, completed just before Larsson's death, are called, in English, The Girl With the Dragon Tattoo, The Girl Who Played With Fire, and The Girl Who Kicked the Hornet's Nest. Even these titles, she suggests, go against Larsson's wishes. He wanted the first book to be called "Men who hate women".

It is a great irony, Ms Gabrielsson claims, that she has been denied her right to safeguard the Larsson legacy – or any share of the immense profits – because she is a woman. Under Swedish law, the rights of an unmarried partner are not recognised. The scatty Larsson, to her obvious fury, omitted to sign a will. And yet, she says, one of the themes of the trilogy is the ill-treatment of women in Swedish society.

"There is misogyny in all this and not only towards me," she says. "In all that concerns [the Larsson industry] women are pushed into the background, even though he worked above all with women."