In a short but perfectly formed biography, Colm Tóibín has rescued Augusta Gregory from both friend and foe

Augusta Gregory was a friend of Henry James and her husband was close to Anthony Trollope: the story of her life resembles a novel they might have - improbably - collaborated upon. But it is also - as she would have wished - a completely and idiosyncratically Irish tale.

The plain and clever daughter of a down-at-heel Big House in the late-Victorian Galway marries a much older man, is introduced to the grand world, and is widowed young.; her literary tastes lead her to the centre of Irish lierary revival, and in the process she discovers her own talents as a playwright, translator and editor. She cofounds a national theatre, gathers a legendary circle around her at Coole Park, becomes a Nationalist and then a republican, survives personal tragedy, revolution and civil war; and through it all, preserves a public hauteur and reticence which conceal a private life of strong emotions and deep passions.

At some time, she cultivated simplicity, and her immediate family saw a very different character. But she was formidable; an old Abbey actor; asked long afterwards what the company felt about her, replied briskly "simple fear". Her distingwishing feature was will-power, not charm. And as Tóibín's title points out, she retained the attitudes of her youth: that there would always be a certain divide "between those who used a toothbrush and those who don't".

But she was much mythologised and perhaps some of this is myth. Yeats constructed much of her reputation, in praise-poems and memoirs, and only recently has her character emerged from the shadows cast by that relationship (described by Micheál Liammóir as "high priestess and sacred snake"). She attracted resentment, because of her background as well as her personality. George Moore famously caricatured her, but Gogarthy was just as sneering in private, jeering at her "farcical" attempts to make Coole "an Irish Bayreuth". Those who think that an Irish Bayreuth might not have been such a bad thing will want to know more. There is now a lively annual symposium in her locality, large scale editions of her diaries and Yeat's letters, and a revaluation of much of her work - as well as the realisation of how much she contributed to Yeat's plays. There has never been a satisfactory full-scale biography, though James Pethica is preparing one.

Colm Tóíbin brief but resonant study is welcome and fascinating conjunction of writer and subject. Tóibín's prose is celebrated for its spareness and intensity; there is an old assonance with the swift almost epigrammatic style which Gregory herself achieves in her diaries and letters, but which often eluded her published prose. His admiration is judicious, and he places her beautifully in the western landowning milieu, which was the back-ground of her whole life. Without adapting the crude argument that the literary revival was an assertions of ascendancy influence by other means, he points out how Coole - which she never technically owned - remained the centre of her world, and shows how cannily she presented her relationship with the tennents (which was by and large good) to best advantage, while preserving some pretty traditional attitudes of her own about keeping the estate solvent.

Tóibín's own interest in the history of the Famine is important here, as Sir William Gregory had introduced the notorious Gregory clause making relief of destitution dependent upon giving up small landholdings. For Augusta, it must have been a skeleton in the cupboard, or the locked room which recurs in Gothic fiction.

Yet her passion for collecting folklore, or rehabilitating local poet Raftery, was real, and so was her conversion to nationalism and her realisation not only that the old order was doomed, but - in her words - "it is better so". Tóibín shows how she could use her hereditary authority, not only to put actors and managers in their place, but to outface Dublin Castle over attempts to censor the Abbey programme: the Viceroy and his officials were "easy pickings" for her. With a novelist's eye for a telling symbol, he foregrounds the "Gort brack" which she traditionally brought to the Green Room for the cast's supposed delecatation: appreciation was strongly mixed with resentment. (Another reminiscing actor described it as "eating a slice of the bog".)

It would be easy to mock, but it is hard to sustain begrudgery after reading her utterly involving diaries, or following through her astonishing fortitude in the aftermath of her only son Robert's death in action in 1918. Tóibín gives this side of her life full due, along with the passionate private life that included love affairs with Wilfred Scawen Blunt and John Quinn (one of her letters to him is reproduced on this book jacket). Perhaps it has taken the most subtle and precisie of novelist to do full justice to the subtelty and precision of Gregory's own character, as well as the ironies of her life.

One of the major ironies was her relationship with Yeats. When they met she was apparently a rich unionist , and he a poor fenian; by the time of the Treaty she was a republican ("without malice", as she put it) and hewas the most conservative of Free Staters. IN the 1920s, he was a senator with a summer retreat near Coole and a house in Merrion Square, where she stayed when she travelled up (third-class) from Coole, which she had leased back when her daughter-in-law sold it to the Forestry Commision; she had hardly any money and he had become grand. The scales had symetrically risen and fallen; while his tactless opinions about her plays, and even more tactless references to her in print, caused some resentment. (Tóibín is very good on the production of Yeat's elegories-to-order for Robert.) But in her last month he moved back to Coole, where he had spent every summer for decades, and saw her out. If he had helped to make her, she had certainly done a lot to make him, and the recognition was mutual. Her death devastated him.

Colm Tóibin has always written with riveting insight about friendships between men and women (notably in The Blackwater Lightship); oneof the few regrets of this book is that he denied himself the opportunity to devote som more speculative attention to this unique relationship. (Did she have an eye to marrying him when they first met? Maud Gonne and Dorothy Pound both said so.) But the point is that Tóibín has decided to relocate Augusta Gregory in her own time and space, rescuing her as much from her detractors like Moore. He has done it with the economy and insight that is all his own.