Hamish Hamilton, stg£10

`People always made up stories about Sonia." So begins The Girl from the Fiction Department, Hilary Spurling's concerted attempt to vindicate the life, loves and legal battles of a woman reviled by decades of literary biography.

Born in India to a spirited mother and a father who committed suicide when she was just four months old, Sonia Brownell was in her early twenties when she first met George Orwell. A strong-willed and independent convent-school graduate, she was working as a secretary for Horizon, the London-based literary magazine.

By the time of their second meeting, Orwell was a widower "struggling with incipient tuberculosis and the care of an adopted infant son." He was gaunt and chronically lonely. She offered to babysit the child.

"The two got on well enough for Sonia to sleep with Orwell," writes Spurling, "more for his sake than for hers, before explaining reluctantly (like all the other girls he asked at this stage) that she could not marry him."

Sonia threw herself back into Literary London. Orwell retired to the Hebridean island of Jura to write Nineteen Eighty Four, basing the character of Julia, the heroine of the book, on Sonia.

The relationship resumed in 1949. Sonia was recovering from the disintegration of a tempestuous love affair with Jean Paul Sartre's rival, the French philosopher Maurice Merleau-Ponty. Orwell was in a sanatorium, dying. She visited him regularly. He proposed again. This time she agreed.

"She made no pretence of being in love with him," writes Spurling, "and, at any rate to start with, acknowledged his need of her far more readily than hers of him. `He said he would get better if I married him,' she told me 20 years later, `so you see I had no choice'."

On January 21 1950, Orwell died of a lung haemorrhage. Days before his death, he had made a will entrusting his literary estate to Sonia, making her his sole heir and offloading on her the responsibility for "enforcing his determination that there should be no biography". They had been married just three months.

Orwell, Spurling contends, put his widow in an impossible position, particularly through the inclusion of the latter provision. She makes a valiant effort to wrest Sonia's reputation from the grasp of those who denigrated her as mercenary and self-serving, who cast aspersions on her lifestyle and ability to manage such a heavyweight literary legacy.

But there is one glaring problem. Hilary Spurling was a friend of Sonia Orwell. A good friend. An ally. "I have tried to pare back what Michael Holroyd called History's cuticle of lies," she writes in the preface. The reading public could have done with a more impartial manicurist.

Spurling's book is not an objective reappraisal of an ostensibly misunderstood woman. Rather it is an angled and defensive portrait, a sketchy volume that sometimes leaves the reader with questions it should have answered, skirting over details that sit uneasily with the agenda of the author, unwisely excluding numbered footnotes and an index.

She does not paint Sonia as a saint. "Fear, suspicion and hostility lay increasingly close to the surface," she writes. "Insecurity or drink released an aggression that made her many enemies."

Nor does she pretend that Sonia didn't guard her literary territory rigorously or withhold copyright permission from writers such as Peter Stansky and William Abrams.

But the enemies, their voices and thorough explanations about why they existed to begin with, are noticeably absent. The opening is a giveaway: it is reminiscent of a kind of playground pettiness. Sonia's social and professional scene was rife with jealousy and backstabbing. Spurling selected her interviewees carefully, excluding those from opposing camps.

In Stet, her memoir about the publishing industry, Diana Athill said Sonia Orwell was, "an intellectual snob without having a good enough mind to justify it."

In Spurling's mind, those who highlighted Sonia's lack of academic qualifications and scholarly verve were themselves intellectual snobs. She counteracts what she sees as their begrudgery or misogyny with numerous descriptions of her subject's beauty and effusive accounts of her generosity, loyalty, application and editorial skill.

"She had luxuriant pale gold hair, the colouring of a pink and white tea-rose and the kind of shapely, deep breasted, full-hipped figure that would have looked well in close-fitting Pre-Raphaelite green velvet."

Strewn with names like Marguerite Duras, Iris Murdoch, Jean Rhys and Ivy Compton-Burnett, the book sometimes reads like an old society column, a who's who of the literati from the 1940s, 1950s, 1960s and 1970s.

Spurling is at pains to show Sonia as more than a literary groupie who was unwittingly landed with an inordinate amount of power. But though she runs through her childhood, contextualising her drives with a brand of homespun psychoanalysis all too familiar in contemporary biography, Sonia, at the end of the book, still seems like something of an enigma.

It's a shame. Her life story is sad; significant only through her link to a great writer of the twentieth century.

Hilary Spurling might not have been the best woman to tell it.