WE ARE talking about the many women in Andrew O'Hagan's life.

Topping the list is his adored 11-year-old daughter, Nell, "whose birth is the greatest thing ever to happen to me, in a sense the only thing that has ever happened to me. Forget the books, the awards, she's my constant delight," he says, showing me a gallery of photographs of this raven-haired, elfin sprite.

Then there's Nell's mother, his former partner and close friend, the writer India Knight, his stage manager girlfriend Lindsey Milligan - "the love of my life - and she's Scottish" - with whom he lives in London's Primrose Hill, and his dear mother Nancy.

Here we must pause, for this magnificent regiment of women also includes the genial 46-year-old essayist and novelist's dozens of friendships. His talent as a writer, who has just published his seventh and most ambitious book, The Illuminations, is almost outshone by his gift for being convivial.

His female friends range from Edna O'Brien and Mary-Kay Wilmers, his legendary editor at the London Review of Books (LRB), where he's editor-at-large, to actress Gillian Anderson, with whom he had supper only yesterday evening because she'd requested his pen-portrait of Tolstoy's society hostess Anna Pavlovna Scherer in War and Peace - she's playing scheming Scherer in a new BBC adaptation. "I'm frae the west of Scotland, pen-portraits are a speciality!" jokes O'Hagan. Recently, he wrote a short film for Anderson, following her award-winning performance in A Streetcar Named Desire. She starred in and directed his prequel to Tennessee Williams's play.

So real and fictional women people our conversation, particularly those in his new novel. The Illuminations is his fifth work of fiction and is already being tipped to win the Man Booker prize, for which he's been nominated twice. Already it has been gilded with golden critical opinions. Meanwhile, there are four offers for the film rights - the BBC is rumoured to be considering a four-part TV adaptation.

The novel begins in Saltcoats, where 82-year-old, Canadian-Scot Anne Quirk is living in sheltered accommodation. Once a celebrated documentary photographer, she's fading into the twilight of dementia. She has an uneasy relationship with her daughter Alice; her needy neighbour Maureen becomes enthralled by Anne's secrets and her evocative photographs. Anne's character is based on Canadian photographer Margaret Watkins, whose marvellous kitchen-sink images and street scenes had long been forgotten when she died in obscurity, in Glasgow, in 1969. As with Anne, a mystery surrounds what cut off an artistic future filled with so much promise.

There have been several exhibitions of Watkins's work and she's been honoured with a Canadian stamp, thanks to the tireless efforts of her erstwhile neighbour, Joseph Mulholland. O'Hagan, who was born in Glasgow and grew up in Irvine, researched her archive in Ontario and has just returned from "talking her up" on his Canadian book tour. "She's due a major retrospective. She was a truly great photographer."

Although we've spoken of Tolstoy's War and Peace -- over dinner in London's oldest restaurant -- another war, another "peace" dominate this interview. For The Illuminations, which was almost five years in the writing, shifts between Anne's memory slowly bleaching out and Afghanistan, where her devoted grandson Luke, a captain with the fictional Royal Western Fusiliers, is on a mission to train Afghan soldiers. His platoon is ambushed; civilians at a wedding party are slaughtered. Deeply troubled, Luke returns home, trying to bleach out his own nightmarish memories. He takes Anne to Blackpool, where she once kept a room, to see the illuminations and perhaps shed light on the darkness in both their lives.

But it's the book's powerful, harrowing contrast between the world of women and art and the brutal world of men at war that is so impressive. "I wanted to write about the home front as well as the frontline," says O'Hagan, who has a first-class honours degree in English Literature from Strathclyde University. "When men - and women - go to war, the women from whom they came are left behind. I know those women. I grew up surrounded by women whose talents were swallowed up by domestic duty - my grannie, my aunties, my mother. They all had so much potential that they didn't get to express. Fantastic, imaginative, coping women. I owe everything I've achieved to my mother.

"There have been many novels about a soldier's homecoming, but I wanted to write one that was right for now and the Afghan conflict. Yes, I do think it was our Vietnam. It seemed to me we had not yet read the book that got inside the problem of that war, what it was like for a soldier, who went off to that war believing in it and came back with all that belief vaporised," he says.

Although, he went to Afghanistan - O'Hagan has been a UNICEF ambassador for 15 years - in 2013, he had already written many of the battle scenes, which you can almost taste and smell. After that visit, he wrote a fearless essay for the LRB about child jihadists. Earlier, in 2008, he'd written about the experiences of British soldiers in Iraq. "I know those working-class boys, that's my background - and I have three brothers," he says. "I grew up listening to lads whose talk is fast, furious, filthy, so I didn't have to research that; I know how lads speak."

Nevertheless, O'Hagan, who was Julian Assange's one-time ghostwriter, acknowledges his debt to members of the Royal Irish Regiment who have been answering his questions since 2010, particularly Andy Allen, a veteran of the Afghan war, from Belfast, who lost both legs and almost all of his sight as a teenage recruit. O'Hagan, whose next book will be a "big, Trollopian epic, with a Dickensian cast of characters," took the unusual step of reading his work in progress to Andy, who was recently asked how he felt about the novel, given that it deals with soldiers who feel betrayed by a war they once believed in.

"He said something that really moved me," says O'Hagan. "He said that he had gone to war so that someone like me had the freedom to write whatever I chose to write. This is a book that deals in facts and with truth. I don't have a political agenda when it comes to Afghanistan, although I do feel it's a failed war. But that's hardly a controversial position. You know, we're very big on heroism but we're not good at treating people heroically when they suffer on our behalf."

In the novel, when Luke returns to Scotland, his mother, Alice tells him he was fighting for his country, the country he was brought up in, with traditions he loved. He replies: "It's a game, Mum. A great game. We only believed in it for as long as it lasted. I love my country for its hills and its inventions, not for its sense of injury, not for its sentimental dream that there's nobody like us. I've been out in the world and I can tell you they are all bloody like us; desperate and tired and fighting for a way into the modern world."

Never afraid to tackle tough subjects - O'Hagan has written about vanished children (The Missing) and child abuse (Be Near Me) - he recently made headlines with a brilliant LRB essay, The Two Lives of Ronald Pinn. He resurrected Pinn, giving him a ghostly online identity in order to expose the activities of undercover police who stole children's names from gravestones and built fake identities, but it would be foolish, says O'Hagan, a past master at creating fictional identities, to assume that Luke shares his views. "I'm a novelist not an editorial writer." He never discussed his own opinions during the referendum, despite countless media requests. "I've never spoken about it until now," he says.

"The thing is I have no sound bites about Scotland. I've always been an essayist and a novelist, but I love the flyting, the ancient Scottish debate, arguing while sitting in the pub cheek by jowl - your face red! - with a man who hates your opinions. I stayed out of the debate entirely because I've lived half my life in England. Shouting the odds about how Scottish people should use their vote is not a good look, neither is it a good luck shouting the odds from Los Angeles or Marbella as my dear friend Sean Connery might choose to do.

"To me, this was a crucial matter for people living in Scotland. As a Scottish man, I was engaged in every second of that debate. It was utterly thrilling to see a generation of Scots also engaged, wanting to throw light onto politics, yes, to illuminate them, and no longer keep people in the dark. I watched and listened with an open heart and open mind."

He pauses: "It wasn't about nationalism at all, it was about a much larger sense of freedom, a sense of fairness, a sense of dignity that the southern politicians in England can only traduce. The nationalists might have lost the war but they won the peace. Nationalism's got my vote, I am all for it - and I don't have a vote! Everything's changed; it's all about my heart now."

The Illuminations by Andrew O'Hagan (Faber, £17.99). Andrew O'Hagan discusses his work at the Mitchell Library, Glasgow on February 19 at 6pm.