Jennifer Egan is sitting in what can only be described as a giant Wendy house.

Moments earlier she was standing next to a skip, posing for pictures while holding an oversized rubber duck. For someone who was listed among Time magazine’s 100 Most Influential People of 2011, it feels a little odd. But then it’s Edinburgh. In August. Strange scenarios are playing out across the city.

The Wendy house in which Egan and I are sitting is actually a mini media tent within Charlotte Square. Egan, dressed in an understated shift dress with a green cardigan, is munching on a salad while doing a bit of name-dropping: Wharton, Eliot, Dickens, Tolstoy – the current superstar of American fiction’s literary heroes.

“I love the swagger and playfulness of 19th-century fiction. It’s regarded as conventional – but only until you start reading it,” she says between bites. (The cadence of her American accent means that, even when discussing death later, her speech is inflected with a natural positivity.) “But it’s crazy,” she continues. “Those authors knew they could do whatever the hell they wanted – and they did. They were rock stars.”

A bit like Egan, then. Only a blue plastic flap separates us from the increasingly noisy crowd that has gathered for her book festival appearance, which starts in 90 minutes; although, she says, she has “no idea” what she’s here to talk about.

Presumably it has something to do with her Pulitzer prize-winning, bestselling novel, A Visit From The Goon Squad, a tight, smart piece of prose so bubbling with intriguing characters, vibrant stories and originality, it even has a chapter formatted in PowerPoint. For those who haven’t read it, this chapter may sound weird – annoying, even – but it’s one of the most poignant parts of the novel; which, in all, comprises 13 interlinked short stories, all loosely set within the music business.

It’s so readable, Egan makes literary brilliance look like a piece of cake. At the risk of sounding sycophantic, I tell her as much. She smiles. “Oh good. As a reader, I really want to be yanked into the story,” she says. “That feeling of having to work and slog – I don’t want to make people feel that way. I want them to feel out of control. My happiest calls and emails are the ones where people say, ‘I missed my subway stop reading your book.’”

Now, having not only scooped one of literature’s top accolades but also beat off Jonathan Franzen’s highly praised novel Freedom to win the 2010 National Book Critics Circle Award, Egan is that rare thing – a critical and commercial success. And the publicity has been non-stop ever since. Is she tired of it? “Maybe if this were my first book, I’d be heaving a sigh and saying, ‘It’s so difficult.’ But this kind of good luck comes once in your career, so to squander it would be insanity. No matter what I write, nobody is going to like it as much as Goon Squad. Even if I top it, I doubt I’ll be rewarded like this. I’m just so happy to have a lot of readers – I’m not used to that.” Egan laughs.

Maybe her attitude is a result of having success later in life, she suggests. Although, at 49, Egan is far from old – and her slight figure and striking cheekbones certainly belie her age – she says that in career terms this might be the pinnacle.

“I know how rare it is, I really do. I can easily see why a younger writer – if it happened for them the first or the second time – would think, ‘This is just how it is.’” She pauses for a bite. “But that is so not how it is – and I know that.”

Although raised “somewhat” Catholic, Egan is not religious. Spiritual, maybe. “To get these kinds of rewards, you have to have the good fortune of having your interests line up with some greater cultural forces – and that’s never in our control. I inadvertently managed to fall into the middle of a moment in which people were interested in something like this – and that’s luck. I know it is.”

A Visit From The Goon Squad is her fourth novel and, as with each of her books, it’s markedly different to its predecessor. Egan – who is also a part-time journalist, mainly as a contributor to The New York Times Magazine – likes to change it up, big style. The plan for her next book is a historical novel set in 1940s New York.

For someone who so embraces change in her work, how does she feel about change in her day-to-day life? “That’s a great question,” she says, raising an eyebrow. “There’s a real disconnect between my writing and my life. I don’t write about my own life and I don’t write about anyone I know. But I do like change and, as a writer, I demand it. But I have a pretty consistent life. I’ve been with the same man for more than half my life. I’ve got two kids. Our lives are really fun and interesting, but not crazy; I’m not looking to turn everything upside down.”

Egan lives in Brooklyn with her husband, a theatre director – her “kindred spirit” – and their sons, Raoul, 10, and eight-year-old Emmanuel. All three are wandering around the book festival while we hide in the tent.

Turning to me, she admits she put off having children for as long as possible. “I was not someone who fantasised about motherhood,” she says matter-of-factly. In response, I tell her I’m wary of automatically speaking to women about motherhood, as if being a parent is a more defining part of a woman’s life than it is a man’s. But the reality is that Egan is a working mother – one minute sitting at home writing her next novel (which she always does by hand), the next minute doing the school run.

Does she compartmentalise work and family? “Not totally,” she replies, “but at the beginning I thought I had to. The first couple of years were hard because I was a workaholic and then there’s this baby. It all seemed so tragic. When I was with him, I felt like I should be writing – and vice versa.”

When Egan had son number two the same familiar waves of guilt flooded back. She didn’t write for a year but, slowly, it got easier. “Now I feel like it’s all one life, one world. I can do both. Maybe the balance was always there and I just couldn’t see it.” I suggest this comes with practice. “Maybe,” she concedes, “but sometimes, when I go from writing to picking them up from school, I’ll feel discomfort; I’ll be aware of feeling unhappy. It’s a sense of, ‘I didn’t get enough done,’ or ‘I don’t feel like being in kid land right now.’ But that ends almost as soon as I’m with them. It is just the transitions that are sometimes still difficult.”

It’s an honest answer. Egan is never what you would call garrulous but she’s forthcoming in that wonderfully American way. Nothing I ask seems too personal, nor does she shamelessly spill private details. It’s as if she’s sifting through the chapters of her life, happily exposing the details relevant to her own story. You sense that, behind the juggling of parenthood and work that is her life, a past is lurking there; she is someone who has lived.

Growing up in San Francisco in the sixties and seventies, Egan listened to The Who and Patti Smith and experimented with drugs: pot, acid, mushrooms. She went to university, then backpacked around Europe – where her eyes were opened to the world around her – before settling on a career in writing, later travelling to China and Russia, and moving to New York in her mid-20s.

Why New York? “A burning desire to live there, a sense that it was the right place for me. I love the diversity, the fact there are so many worlds in New York and most of them don’t get a damn about what I do and my world. I love that.” Egan thrives on the anonymity of the city, eavesdropping on the conversations of others on the subway. “It’s full of little dramas.”

But what of those life-changing moments? “I’ve had a few like that,” she nods. “Finding out loved ones are dead …” She trails off, puts down her fork, then smiles. “Winning the Pulitzer – now that was the happy inverse, when you hang up the telephone and think, ‘I have a piece of information that’s going to rearrange my life.’ I’d only known it the bad way before.”

One day in her early 30s, Egan was eating a pumpkin muffin when the phone rang. It was her uncle. Her father, who had just turned 60 and was in perfect health, had been killed in an accident on his bike. “That was one of those moments. I know what a phone call like that is like. And you think, ‘Before that phone call, I thought everything was fine.’ I go back to that day. It had such an axis of before and after to it.”

There’s plenty of before and after in A Visit From The Goon Squad, which moves between the past and the future, but Egan never gives the reader that dramatic moment in the middle. “You shouldn’t need to,” she says. “In a way, those moments are all alike. The interesting part is the ramifications of them.”

In her own life, this equates to living in the moment, appreciating what life is offering now, not later. “You don’t know what will happen and you never want to look back and say, ‘I wish I’d realised how precious this was.’ I try to realise it every minute. You asked earlier about whether I seek change …” She adjusts her seat to face me better. “I don’t, but I’m aware it can arrive at any moment, often in an unpleasant form. It just comes. Things happen. People get ill. People have problems. You just don’t know. I’m hyper-conscious about the possibility of change all the time. But I don’t think I lose anything by that – although I can sometimes be very anxious.”

So one day recently, when one of her sons woke up complaining of a “pounding pain behind his eye”, Egan ushered him straight to the doctor. “I’m picturing brain tumours, thinking, ‘Is this the before-and-after moment? Will everything change today?’” Thankfully, her son was given a clean bill of health and Egan’s readiness for the world to be transformed played perfectly into the boy’s desire to avoid camp and have a day with his mother. She chuckles at the memory.

For her own part, Egan experienced tumult in her early life. She has no memory of her parents being together – they divorced when she was two years old – and with both parents remarried and living in different cities (she moved from Chicago to San Francisco with her mother and stepfather), she was always the stepchild.

“There were a lot of times when I was looking for a security that wasn’t there,” she says. “It gives me such delight to have one of my kids want something and to just … be there. I think, ‘Wow!’” Egan worries about when that may change – when her children’s visceral need for her is no longer there.

Motherhood aside, does Egan believe there are challenges in being a female writer? “It’s hard to know,” she says, flicking her blonde hair over her shoulder. “I’ve had plenty of attention for my work” – the gathering crowd waiting outside for her testifies to that – “but when I made my break from a more conventional kind of work, in my third book, Look At Me, I was aware I was doing something I didn’t really have a model for – and I felt terrified.” Looking back, Egan believes she had internalised a view that she, as a woman, wouldn’t be appreciated for that kind of work.

In fact, the book – an ambitious, somewhat surreal intellectual thriller about a model whose face has been destroyed and rebuilt – went on to make the short list for the prestigious National Book Award.

“But my sense of those limitations – or limited expectations – had something to do with being female,” she continues. “And I think that’s dangerous – the ways in which we censor or limit ourselves based on what we believe to be the culture’s expectations of us.”

Egan mentions the author VS Naipaul who, two months before our interview, made what some would call sexist comments regarding female authors, suggesting they can’t – or don’t – write ambitious work. His comments have stuck in Egan’s mind. “The fact he would say that – and that we would recognise that as a point of view – alerts you to the fact the idea exists.

“He sounded ludicrous, everyone knew it and it was an idea that sounded stale the minute it left his lips; but at the same time, it’s not something we’ve never heard before either.” Egan could do worse than send him a copy of her next book.

But in a way, she says, “I feel the good luck with Goon Squad has been so colossal, I know my next book won’t be as well received – and that’s sort of a relief. It’s like I don’t even have to wonder about that. It’s a done deal. Now let’s just do the best I can.”

Egan is, then, an optimist. There may be some worrisome forces at play in the Orwellian final chapter of A Visit From The Goon Squad, which is set in the 2020s, “but the people are still good people”. She pauses. “I don’t know anyone who’s not scared of the future, but I have a lot of faith in human beings,” she says. “There’s luck to the very fact this planet exists and I hope we can sustain it. We don’t realise enough how miraculous it is.”

Time is a goon, as it says in the book, but Egan is excited about the future. “What I really don’t want to do is settle into any kind of groove,” she smiles. “That’s never been my way.”

A Visit From The Goon Squad is published by Corsair, priced £7.99.