In Quinn’s The Whalebone Theatre (Knopf, Oct.) an English girl stages plays with friends and family in a whale’s rib cage after WWI, then becomes a spy in France during WWII.

How did you happen on the idea of a theater constructed from the ruins of a whale?

I read a nonfiction book called The Wreckers by Bella Bathurst, which said whales that wash up on English beaches belong to the monarch by right—it’s an ancient law. I liked this fact, as it touches on themes of entitlement and tradition that I was interested in exploring in my novel, so I included a stranded whale. But I didn’t think to turn it into a theatre until I went to see Kate Bush live in 2014. She had a stage set that looked like a whale’s rib cage.

Did you deliberately decide on playacting as a thematic through line?

It evolved quite naturally out of thinking about both social expectations in the English class system—which relies on people performing certain roles—and about childhood imagination, which so often includes pretending to be other people.

Why do you think so many contemporary English writers are revisiting WWII?

For me, it is history within touching distance—my parents were born around that time—so there is a personal interest. But I am also fascinated by social changes brought about by larger historical events, and WWII seems to be almost the hinge of the 20th century. So much changed from pre-war to post-war, and we still feel the ramifications of those changes.

The Whalebone Theatre took you 10 years to write. How much of your vision of it changed over that time?

When you start a book, it is a perfect abstract thing of wonder that exists in your mind as a gleaming citadel made of clouds. The writing journey is the process of letting go of that glorious apparition, and building your own, smaller, wonkier replica out of tiny handmade bricks. It feels humbling, but in a good way. It’s a bit like running a marathon, you start off dreaming about crossing the finish line in a blaze of glory, and you end it just praying you’ll get there in one piece.

Why did you decide to go big with a decades-spanning, jam-packed narrative?

I think I just naturally gravitated towards that style of book because I like to read them myself and because coming up with lots of characters and depicting different eras is so much fun. It felt like play to me.