How deep do we want to go then?

"Isabelle found a vacation snapshot of her boyfriend's ex-girlfriend. She ripped it up and left it in a neat pile on his pillow." How far do we want to dip our hands into the deep pools of jealousy and insecurity? "Owen was Agnes's ex-boyfriend. He had introduced her as his 'friend' one too many times."

On a New York morning, just seven weeks after the arrival of her daughter Thomasina, Leanne Shapton is sitting in her former office – now a nursery – thinking back through the murk of memory to old boyfriends. Thinking back to the shadows left by their past girlfriends, whose pictures or clothes or name were still present when a new relationship began.

"Let's see what I can cop to. Umm, the photo left on the pillow is a friend of mine. I dropped a picture of an ex-girlfriend behind the piano so it couldn't be retrieved. This really heavy piano. That was at the Chelsea Hotel -" She flicks through her book Was She Pretty?, a stiletto-sharp collection of words, pictures and collected miseries, and chances upon one in particular. "Claudine had a small emergency in the middle of a romantic dinner at her new boyfriend's apartment. To her relief and equally dismay, she found a box of tampons in the medicine cabinet."

"The tampon story is mine," Shapton admits. In fact, she reckons, putting the book down, maybe 60% of the material in the book comes from her own experience. "Sometimes they're the same relationship, different ex-girlfriends."

It's almost ancient history now, it should be said. Was She Pretty? was originally published seven years ago and a new edition has been issued in the wake of the success of Swimming Studies, Shapton's cool-toned, chlorine-perfumed memoir of her days as a wannabe Canadian Olympic swimmer.

Was She Pretty? came out of a series of drawings she did back in 2001. "I was dating somebody and I had to deal with my feelings of jealousy. The book was published in 2006 and since then I've given the book to girlfriends of mine who have reached that stage in a relationship too. They come over and we go for a drink and they go, 'I want to look at his emails. How do I deal with it?'

"What I found researching the book was how fun it is to talk about this stuff – because I felt so awful about my jealousy. I wouldn't even admit I was a jealous person. But then when you find someone who has similar feelings about these things you've done, these weird passive-aggressive moves, like body-checking someone at a party, it's really, really fun to talk about. In a way I wish I hadn't waited until my late 20s and early 30s to talk about this because it's funny and relieving." And, she adds, it's an excellent conversation starter at dinner parties.

Is there a gender difference about such things? "Yes, I think there is. With men it's about territory or something. There's kind of a possession thing. And with women it's more about themselves. It's more about feeling bad with men."

It feels like a very New York book in a way – clever, brittle, funny – the kind of thing you'd expect from one of the city's cool girls, a girl who has written for Elle Magazine and publishes a painting each month in the New York Times. Swimming Studies, in contrast, has some of the wide open space of her Canadian birthright. What both share – as does her other novel, Important Artifacts And Personal Property From The Collection Of Leonore Doolan And Harold Morris, Including Books, Street Fashion, And Jewelry – is the combination of words and image.

Perhaps that's to be expected from a former art director of the New York Times op-ed page. "That is kind of how I see the world," she says. "Essentially after working as an art director, where you're understanding how people read images and pairing that with language which I love – I've always been a huge reader – I kind of want to keep working that way. I'm playing with all that stuff."

Visual literacy is changing quickly, she thinks. I wonder, though, if she met any resistance to the idea of words and pictures together from publishers. "Well, no. People saw it as a novelty." That said, if she tells people she writes and draws they say: "Oh you're a children's book writer."

She's not a graphic novelist. Nothing is placed in panels. But, interestingly, when she came to work on Swimming Studies it was to graphic novels she looked for literary inspiration. "This is a terrible generalisation, but a lot of traditional memoirs are about overcoming strife. 'This terrible thing happened to me and this is my story.' Whereas when I was thinking about Swimming Studies nothing bad happened to me. I was a privileged Canadian. My parents could afford to give me swimming lessons and I trained.

"So I was looking more to the voice in graphic novels, which was more a suburban ennui. 'I'm an outsider. I'm a geek.' It wasn't necessarily this story of redemption. It was this almost navel-gazing thing I was fascinated by. I was looking at the girls who talked about high school and the boys who talk about superheroes, and that helped me feel that I had a story to tell with Swimming Studies. Swimming Studies is really a suburban story."

The result – a reminiscence of early Ontario mornings, damp swimming costumes, greedily scoffed candy bars, long bus journeys and open water – is a synaesthetic probing of the watery course of her younger years when she swam competitively and was good but ultimately not good enough to swim for her country, as well as the waves that those days sent through the years of her life since. (Even now when she dreams about water, she says, it takes the form of a pool.)

Curiously, Glasgow swims into focus at one point, a brief, vivid pen portrait of Shapton eating peanut butter in one of the city's parks while visiting on her own back in 1991.

"I wanted to go to the Glasgow School of Art so badly. I visited and I guess there was a student show on and I just fell in love with Glasgow. I was staying in a hostel. I'd ditched my friend. Well, we probably ditched each other. I remember being in Glasgow alone which was weird but the romance of the Mackintosh - just getting completely seduced by all of that, and going 'OK, I want to go to art school'. I was still too shy to eat in restaurants alone so I bought peanut butter and I had a plastic spoon. I don't know what park I sat in."

She's hoping to return one day. But in the short term there's the small matter of a new baby and two more books to negotiate. Later this year she will publish Sunday Night Movies, a book of paintings inspired by the movies. She's also working with Sheila Heti and Heidi Julavits on a book called Women in Clothes.

"It's about the psychology of dressing our insecurities and the weird compulsions we have and the choices we make. There's one thing I'm doing for the book called Dressing Maps, where I'm taking a picture of my floor after I decide what I'm wearing because the floor is just strewn with all of my rejects. And then I'm drawing a map of that and itemising why that thing was tried on and the thought processes behind that. It's not something that gets talked about in fashion media, in Vogue or these magazines. That's a completely different planet."

And that's the future. The past is already on the page. Oh, and as for the boyfriend whose exes' ghostly imprints first stirred Shapton's own passive-aggressive tendencies? Reader, she married him.

Was She Pretty? by Leanne Shapton is published by Penguin, priced £9.99. Read tomorrow's Sunday Herald for an interview with Gilbert Hernandez, of Love And Rockets, who'll be talking about his new book Marble Season, and for Teddy Jamieson's round-up of the best new graphic books