On our way in to breakfast - and the Irish Times interview - Susan Sontag stops to engage in conversation with a woman she has never seen before. We are in a remote hotel in the Welsh mountains, where Sontag is staying during the Hay-on-Wye literary festival. First she begins by admiring the view, the idyllic setting. Then come the questions: Where does the stranger come from? Why is she here? Even though the woman clearly has no idea who her striking interlocutor might be, she answers. The intensity of Sontag's gaze, her face still luminous with the aura of past beauty, topped by a Bohemian tumble of black hair, gives her a natural authority.
"Please forgive me," Sontag says when we finally sit down. "But it was just so incongruous. Seeing that woman - how do we say these days? - an American of African extraction, in these surroundings. I had to talk to her. After all I am a novelist."
Of the many adjectives used to describe Susan Sontag over the last 40 years, novelist comes way down the line after intellectual, essayist, feminist, anti-Vietnam war campaigner and cultural guru. Although her first published work was a novel, she soon "drifted off", she says, into writing essays. "I still like my early novels, but I didn't have wings. I couldn't fly." Whereas in the rarified atmosphere of 1960s New York, the sky was the limit for the beautiful young academic who could talk as well as write on everything from Levi-Strauss to high camp. "These essays were enormously influential, appallingly influential. I just wanted to whimper, I'm a novelist. I'm a novelist. But it was the essays that people were interested in. And I kind of lost my nerve about fiction."
Sontag is now dismissive of the "insufferable moralism" of her writing at that time, and acknowledges that vanity had something to do with its appeal for her. "It was kind of seductive to be part of the public debate about things, and to feel that one was supporting the good, the true, and the beautiful, turning people's attention to wonderful things that they might not know about."
But she was never entirely at ease. "An essay is one-voiced, while the novel is multi-voiced and multi-perspective. It is only in the novel that you have scope. But I had to figure out a way to write fiction, fiction that would tap into things that I knew and felt." Surprisingly, perhaps, the answer turned out to be fiction set in the past. And in 1992, after a gap of 25 years, The Volcano Lover, a triangular story of William Hamilton, his wife Emma and her lover Horatio Nelson proved a worldwide bestseller.
In America, published this week, follows the fortunes of a Polish actress who takes America by storm in the 1880s. Like The Volcano Lover, the story is based on a real story Sontag came across by sheer chance, while browsing in a Boston bookstore in an academic monograph about the Polish author of Quo Vadis?, Henryk Sienkiewicz. "I saw that as a very young man he had accompanied a great Polish actress Helena Modjeska to America and that they had gone to Anaheim California. And I thought, what a story. I just knew that's it. That's the next novel."
She dismisses as "preposterous" recent accusations of plagiarism raised by the Modjeska Society in Anaheim: "of course I used primary sources - a couple of anecdotes and a section of an interview. I always said it was based on a true story it is nothing to do with plagiarism."
Sontag found writing through the medium of the past intensely liberating, allowing her to be "operatic and expressive and romantic", not qualities immediately associated with the woman dubbed by Jonathan Miller "the most intelligent woman in America"; but Sontag also turns out to be touchingly vulnerable.
A month or so back she was sent a clipping from a respectable English newspaper, under the headline "Old Skunk-head changes her spots". The inference being, she explains, "that wasn't it odd that this `great intellectual' had changed direction by writing a historical novel". While the "historical novel" tag merely irritated her, Old Skunk head - referring to the natural white streak in her hair that until her recent chemotherapy for uterine cancer was the Sontag trademark - was harder to dismiss. "I know you will laugh," she said, "but I felt hurt. Really hurt."
Susan Sontag was born Susan Rosenblatt in 1933. Her father was a fur trader and, until his death from tuberculosis when Susan was five, her parents lived most of the time in China while Susan and her sister were looked after by a succession of relatives and an Irish nanny called Rosie. After her father's death the family moved repeatedly, first to New Jersey, then Florida, then Tucson. When her mother married again they moved to California and Susan took the name of her stepfather.
She has described her childhood as "a long prison sentence". A succession of "wretched public schools" failed to dim Sontag's love of language and books - she saw herself as Dorothea Brooke, the high-minded heroine of Middlemarch. From North Hollywood High, at 15, she "propelled" herself into "probably the best university education in the planet". First to UCLA, then Berkeley, then Harvard, then Oxford. However, Sontag's personal self-esteem was less secure. She married at 17, 10 days after meeting her future husband, a sociologist - Casaubon, she says, to her Dorothea. The marriage lasted nine years. "I knew that the decision was weightless, because when I said `I do', I felt like laughing." She doesn't regret it, because of her son. "But I guess I wanted to be stopped, because when I rang my mother up and told her she said `What's his name?' And I remember thinking `Shit, she's not going to stop me'.
"I felt an enormous inhibition because of my mother. She was only five foot four and I was, for then, very tall, so right away I'm this awkward gangling person." Her mother was "famous for being beautiful". Only many years later when looking at some old photographs did the truth dawn on her. "I thought, `If I didn't know it was me, I would think this person was good looking'. And mediated by the pictures I allowed myself to acknowledge that I was good looking." She certainly didn't use the word "beauty", she insists. "I was truly dismayed and horrified when people would say, `it's not fair - you're beautiful and clever'. My first reaction was `I can't help it'. I just felt so awful."
While her often absent mother was "very withholding, unmaternal, laconic", her surrogate mother Rosie was warm, funny and "a great babbler". "She was a monologist. She talked as if there was no full stop. The full stop was just a comma. She is my idea of garrulousness, and the music of it is absolutely in my head." It is also in both The Volcano Lover (the posthumous monologue from Mrs Cadogan, Emma's mother) and more obliquely in In America: two of the three monologues in the book are written in full-stop-less mode.
Sontag's love of the theatre and actors is longstanding. Great acting is about the ability to change yourself, to transform, hence the parallel exploration in the novel of these two arenas of transformation, the theatre and America itself. "I have lived a lot of my life in the world of theatre and film, I love actors, I love what they do, it's difficult, and I'm in great sympathy, they're very tormented people."
In her youth Susan Sontag acted both in student productions and in summer stock. She has written one play (Alice in Bed, about Alice James, sister of Henry) and is a well-known theatre director, though her most high-profile production, at least this side of the Atlantic, is undoubtedly Waiting for Godot in Sarajevo. She first went to Bosnia in 1992, primarily to visit her son David Reiff, a writer and journalist who was covering the war. "I was terrified he would be killed," she explains. "And I wanted to see what it felt like, and what he was going through." She knew the head of the George Soros philanthropic programme, and he agreed to take her with him.
It was, she acknowledges now, unbelievably dangerous. Sarajevo appalled and moved her. She had to do something to help, she said - but what? The decision to stage a play was nothing to do with her, she insists. "I wouldn't dream of saying, `Oh I am going to Sarajevo to do theatre', it would be unbearably pretentious." She could type, she said, or do some paramedical things - as a child she had wanted to be a doctor and was "medically literate". Writing she felt wasn't any help. But when she mentioned theatre, their eyes lit up. "We have lots of actors," they said. Journalists there at the time remember her nightly scouring of the Holiday Inn for unwanted bread for her actors.
The choice of Waiting for Godot wasn't difficult, though the humour-in-grimness inherent in the play, was given added weight when the company took to calling it Waiting for Clinton. "That was awful," she remembers. "I said, `I don't think the cavalry are going to come over the hill and save us'." They didn't believe her.
Her eyes improved through having to use them at night. She stood in line for water, learnt to sleep without glass in the windows, to the sound of sniper fire; learnt fear. She remained in Bosnia on and off for three years. For them or for her? For them, absolutely. "But I suppose there is a part of me that wants to lose myself. I think it's why I like being a foreigner. Being a foreigner you are a little bit invisible. They may be polite, but they don't really pay attention to you. You become anonymous. People say, `Oh, you like travelling.' But the travelling itself is a drag. I like the intensification of one's own consciousness. Sarajevo was unbelievably unsettling, but it was so intense. I feel privileged to have been there. It was one of the great transforming experiences of my life. I believe in transformation. It's the way I want to live, it's something I very much admire. It's the most American thing about me."
In America by Susan Sontag will be reviewed on these pages next week