Ahead of her latest, unnerving novel Sisters, the youngest ever author shortlisted for the Booker discusses her fascination with horror, family and growing up on Harry Potter

Daisy Johnson and I are talking about compost. She never thought she’d write about the Fens, she explains, but she ended up revisiting her childhood landscape in her debut book, a short story collection that won the Edge Hill short story prize. She also didn’t anticipate reworking the Oedipus myth that had so enthralled her in her schooldays, but it formed the bedrock of her first novel, 2017’s Everything Under, which made her the youngest writer, at 27, to be shortlisted for the Booker prize. “Maybe it’s just time,” she ruminates, “and maybe the things I’m reading now will circle back in 10, 20 years … I sometimes think of ideas as a sort of composting and that they just need to compost for long enough, and then you can think about them and write about them.”

But the thing with compost, I say prosaically, is that you have to choose what to put in, when to add water and to turn the heap. Johnson likes that idea, and firmly says she’s not the kind of writer that turns away from reading fiction when she’s working on her own books, or steers clear of anything that feels too similar. She is, instead, a magpie, of the belief that “nothing is sacred, and I think we should take everything that we possibly can and make it of our own and send it out into the world”.