Back in 1978, everyone was reading The World According to Garp, the story of a wrestling coach and his feminist mother that played out like a Greek tragedy. As a teenager, I was most struck by a casual scene where the wife reaches out and grips her husband’s soft cock while they lay in bed. The moment says so much about intimacy between partners. I couldn’t wait to grow up and have that for myself.

John Irving has always been a cutting-edge storyteller. The 70-year-old author is currently promoting his latest novel, In One Person, about a bisexual man who falls in love with a transsexual. That’s only part of the story. He also has male and female lovers, a crossdressing grandfather and a father who lives as a drag performer in Europe. There is literally something for everybody under the queer rainbow.

The novel provides a sharp picture of small-town life in the 1950s and a harrowing depiction of the onslaught of AIDS in early-’80s New York City. Protagonist Billy Abbott is supremely self-confident about his bisexuality — a portrait at odds with the common perception that bisexuals are confused.

“Most of the gay men of my generation did not believe guys who said they were bi, presuming that they were gay with one foot in the closet,” says Irving during our meeting in Toronto. “To straight women you were doubly untrustworthy, and for most straight guys, you were just gay. But I’ve written characters like John Wheelwright [in A Prayer for Owen Meany], who never has sex, or Dr Larch [in The Cider House Rules], who has sex once and never again, or Jenny Fields [in Garp], who has sex with a comatose man and never again. I find those decisions a hell of a lot more strange than having sex with men and women.”

Irving believes in the importance of sexual liberation, but the book makes a point of saying that we are more than just a label. “Sexual identity surely matters, but it can’t be used as a superficial means for other people to define us,” he says. “Just because they know our sexual identity does not mean they know how we feel, and it is often said derisively, as though it gives us some conclusive truth about that person.”

Some of Irving’s novels have gone on to become movies: The Hotel New Hampshire and The Cider House Rules, which won him an Academy Award for Best Adapted Screenplay. Still, Garp remains my favourite. When I bring up the many similarities between Garp and Irving’s most recent book, he reminds me that “Garp was much more radical, politically extreme and satirical. The portrait of feminism was exaggerated, and Roberta [the transgender character] is brave, but comic. The new book is much more realistic, gentler. I was younger and angrier in 1978 and painted with a broader stroke.”

So I had to wonder why John Irving, a straight man, feels so strongly about gayness. “Twelve years ago, when this novel was waiting to be written, I did not know that I had a gay son. My youngest son, Everett, came out and I was proud of him, but I don’t want anyone to say I wrote this novel because of that. In May of 2009, when I was looking at which novel I would write next, it’s unquestionably true that I hoped it could be this novel because I had an ideal reader. I wanted Everett to be able to read this story while he was still a young man. There’s a difference between writing a novel because of someone and writing a novel for someone.”

All the same, it’s very flattering, especially when the novel in question is as good as In One Person.