Shirley MacLaine read her palm and saw "mother and prostitute, many times".

An oral swab revealed she shares DNA with Marie Antoinette, the Tsarina Alexandra and Susan Sarandon. You'd have to say that palmistry wins out over genetics, certainly when it comes to pinning down Edna O'Brien's essentially divided nature, if not her occasionally preposterous grandeur and sense of theatre.

Half of Ireland likened O'Brien to a prostitute when The Country Girls, her first scandalous novel, came out, but most of us still tend to forget that behind the colour supplement glamour and TV persona – an early, flame-haired version of Nigella whose entendres were ruthlessly single – there was a woman with children, a mother who cleared space at a table and wrote, or made secret spaces for imagination. The trope takes shape with Virginia Woolf, who shadows the present book in significant ways, and resurfaces in JK Rowling, who seems as retiring as the Blessed Edna is bold but who might well find much in common; if, that is, they aren't friends already, since Edna seems to know and name just about everyone.

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She vowed she would never write a memoir. One rather assumed she already had, with The Country Girls, The Lonely Girl, the savagely titled Girls In Their Married Bliss and August Is A Wicked Month, which my grandmother confiscated and then burned, purely on the strength of the Snowdon cover. It was felt, too, that Mother Ireland was a kind of autobiography and its attendant documentary a fairly public working-out of the relationship with her own mother and father, who has become the type of drunk, contrite, fistful, maudlin Irish fathers.

The early chapters of Country Girl read very much like a lost "early O'Brien", but there is a touch of autumn too. The younger Edna would have admitted (just) to lines on her palm, but never on her face. The creak of mortality runs through the new book, with talk of hearing aids (discarded) and a replaced hip. But there is plenty of racy and self-exposing stuff, too. Her husband Ernest Gébler comes out of it badly. The two boys, Carlo and Sasha, come out of it well, if rather precociously. There is a fling with Robert Mitchum; what might have been a fling with Paul McCartney (who comes home with her and serenades the boys with a Mary Hopkin song); there is a shy kiss from Norman Mailer in St John the Evangelist church, and a bolder one from Jude Law. There are two main affairs, with Jay and "Lochinvar" (who presumably might ride out of the west with a writ) and they are scorchingly believable.

Lawrence Durrell didn't read her palm, but looked for a single breast, implying she was an Amazon. O'Brien provokes this kind of blunt gallantry in men. Seamus Heaney leads the charge in this, arguing that her great strength has always been an ability to give hurt the same psychic and imaginative value as joy. O'Brien recognised this herself in the still spinning wreck of her marriage, at a point when she seemed as likely as Moll Flanders to win custody of her children (she did, though), when a new novel came to her entire. "That is the mystery about writing: it comes out of afflictions, out of the gouged times, when the heart is cut open."

It's fair to guess that many of her readers will not be aware just how deep the afflictions were or how deep and surgical the cuts. Surprisingly, perhaps, the man who looms largest of all in the book is O'Brien's sometime therapist RD Laing, the sage of the divided self. He dances onstage like a keelie Nijinsky, sleeps on the grass, and later administers LSD. In the first lysergic flash, O'Brien sees him as a rodent in a suit. Dreams and visions are very important in this book, and this one is central. He abandons her in the midst of her trip (the rat!) but it is Laing who oversees her transition, in the massively underrated Night, from mnemonist to real writer.

The jury – or at least an academic jury – is still out. They haven't quite forgiven her in Ireland, and she made things more complicated by writing later about the IRA, albeit seeing quite through the Jesuitical Gerry Adams. No one much admits to liking her, except her loyal readers; Mrs Grundy thinks she's a hussy and a homewrecker; "Feminists and academics ... [tear] into me for my supine, woebegone inclinations." A generation of critics has tended to deride her as a come-after and a populariser, the relict of Ireland's great literary moment with Yeats and Joyce, Synge and O'Casey. But she is no more after-the-fact, anglicised or blandly cosmopolitan than Heaney or her one-time champion, JP Donleavy, and she is much closer, in person and literary spirit, to Samuel Beckett than usually acknowledged.

It's tempting to think while reading Country Girl that writing is something that goes on between parties, love affairs, shopping and therapies, when the opposite is unmistakably the case. She spends a dull but very "Edna" Christmas in hospital. A foreign nurse sees the notebooks and begs, "Madam, please write book for men about love because they do not understand it as women do". Which is exactly what she has been doing for 50 years. It has been rather fine to know her.