Richard Flanagan, 63, lives in Tasmania, his birthplace. His sixth novel, The Narrow Road to the Deep North, which drew on his father’s experience as a Japanese prisoner of war, won the 2014 Booker prize and is about to become a TV series starring Saltburn’s Jacob Elordi. His latest book, Question 7, is on the shortlist of this year’s Baillie Gifford prize for nonfiction (to be awarded on 19 November), having also been shortlisted for France’s Prix Femina Étranger, a prize for novels. For the Spectator, it “uses an eccentric toolkit – part memoir, part history, part fictional imagining – to produce a book quite unlike anything else”; for Peter Carey, it “may just be the most significant work of Australian art in the last 100 years”.

How do you feel about Question 7 being up for a fiction prize as well as a nonfiction prize?
Delighted. Labels are for jam jars.

What led you to write it?
A mistaken diagnosis of early onset dementia in 2022. I was given at best 12 months before it would begin in earnest. In those 12 months I wrote the book. When done, I asked my editor if it showed any signs of cognitive collapse; if it did, I didn’t wish to see it published. She began laughing. The neurologist subsequently confirmed her opinion.

Which of the book’s many threads came first?
Once I had the idea of writing the book as a chain reaction that begins with Rebecca West kissing HG Wells and leads to 100,000 people dying in Hiroshima, my father living and me being born – once I understood that without that kiss, there would be no bomb and no me – then disparate things that had haunted me for so long fell into place. I thought much about my parents who, in a world they knew to be meaningless, nevertheless asserted an idea of love as their answer to the horrors out of which my island home is torn.

Wells’s novel The War of the Worlds is pivotal to the narrative. Do you remember the first time you read it?
I thought I knew the story – yet when I first read it, perhaps 20 years ago, I was staggered to learn in Wells’s introduction that it was inspired by the extermination of Aboriginal Tasmanians. It isn’t a hokey Edwardian set piece. It’s an indictment of English imperialism.

Are you a restless writer? Your books are similar to one another mainly in their difference …
I’m easily bored. And then there’s age. I seek forms that account not just for what’s lost but reflect what’s gained.

Were you inspired this time by the discursive turn that English-language fiction has taken since WG Sebald?
Fashions come and go. With this book, what mattered above all wasn’t literature, but life. During Covid, life for us all seemed on hold. The question I was left with was: do we wish to live, or are we content just to exist? And I think that question haunted many.

Do you think you’ll go back to writing novels of plot and character?
I am not sure if I will write again. Whatever impelled me for so long has left, for now at least. Perhaps I’m just happy to be in the company of friends and family.

What’s your role in the forthcoming TV adaptation of The Narrow Road to the Deep North?
Executive producer. I’m not interested in a literal act of fidelity to my novel. I wanted to get a director I respected [Justin Kurzel] and let him make his own work inspired by whatever he found in mine. I saw my job as supporting Justin.

The lead is Jacob Elordi. What did you make of Saltburn?
Saltburn is the one film of Jacob’s I haven’t watched. I wasn’t so enamoured of Oxford [where Flanagan was a Rhodes scholar in the 80s] as to be fascinated by its fictional representations.

That period in your life comes up in Question 7, where you encounter a thinly veiled Boris Johnson …
Few things exemplify the vacuity of 1980s Oxford better.

Question 7 also mentions that The Wind in the Willows was one of your favourite books as a boy. Why?
I think because of my mother reading it to me. She loved it and I loved her. We lived in a very remote, small mining village full of postwar refugees in the middle of a great rainforest, rain and rivers everywhere. The idea of a river joining very different people, of people having homes in the wild woods… it all seemed somehow familiar. She didn’t skimp the more difficult language or chapters – the mystery of it seemed the mystery of the world beyond.

Name the first novel that made an impact once you were reading yourself.
Camus’s The Outsider, at the age of 11 or 12. It was on a spinner of books at the state high school where I had just started. I picked it because it was skinny. I understood almost none of it. But the heat, the beach, the abrupt violence, a world that demanded your hypocrisy… all that, I knew with a shock of recognition, to be true.

What are you reading right now?
Erotic Vagrancy, Roger Lewis’s addictive account of Elizabeth Taylor and Richard Burton. Will we be so enchanted by Tay Tay and Kelce 60 years hence?

Australia’s National Portrait Gallery holds a 2018 painting of you with your parrot, Herb, who was previously seen perching at your desk in a short film that the New Yorker made about you. Is he still there?
It’s hard to imagine Karl Ove Knausgård with a macaw or Sally Rooney with a sulphur-crested cockatoo, but every writer needs a Herb, a marvellous companion of inestimable humour, who to get my attention once flew on to my keyboard and beating his wings deleted a chapter; who danced and strutted while screaming “get fucked” every time the phone rang; who shredded my books and furniture and would fly on to my chest to be hugged. Now he’s gone. I still grieve.

• Question 7 by Richard Flanagan is published by Chatto & Windus (£18.99). To support the Guardian and Observer order your copy at guardianbookshop.com. Delivery charges may apply