Katherine Rundell’s characters are in perpetual motion. They can be found cartwheeling in thunderstorms, as in her debut children’s novel; scaling Parisian buildings in her fairy tale–tinged Rooftoppers; charting a perilous course through the Amazon in her survival story The Explorer; and corralling a multitalented crew of kids and animals for a high-stakes heist in her Jazz Age Manhattan–set caper The Good Thieves. Raised in Zimbabwe, Belgium, and England, the author currently lives in Oxford, where she is a fellow of St. Catherine’s College. In between research and teaching, she engages in her own derring-do, including tightrope walking, rooftop climbing, and piloting a small plane.

You give a child a house and they make it into a castle as they read.

Rundell also carves out moments of comparative stillness to write globe-trotting adventures for middle graders (see above) and books for adults, including Super-Infinite, her recent biography of 17th-century poet John Donne (more on him later). “My rituals really are around reading,” she says of her creative process, speaking via Zoom from her office in Oxford. Lined with bookcases, one could imagine it opening into a secret portal. “I spend a lot of time in the archives. I have access to the most wonderful libraries at Oxford, which is a gorgeous stroke of luck for me.” In particular, she seeks out “books that will sound the note that I want, like a tuning fork—and that is often poetry.”

If she’s crafting a scene that’s “big and bold and emotional,” for example, she might dip into the romantics or the metaphysical poets. If she’s writing something “a little bit sharper,” she says, “maybe I’ll read some Frank O’Hara. Because I find that poetry has that mixture of language and music, which can liberate your own imagination into slightly different tones. And I find that is a helpful way to kick-start a writing day.”

It was an unfinished epic poem by Donne, titled “Metempsychosis” (about the transmigration of a soul, reincarnated in various forms across the centuries), that sparked the concept for her Impossible Creatures series. “I loved the idea,” she says. “What if that soul was, when we meet it, a girl? What would that mean?” The book also asks the question, “If you could look at us, in our full sweep—all our love, and all our wit and warmth and generosity, all our care, all our invention, and all our rage and destruction and murder and cruelty—what would you say of us? Would you say mankind is not worth the pain it visits on itself? Or would you say, on balance, yes to humanity? Would you say that, despite our flaws, we are nonetheless a miracle?”

The first book in the projected series debuted in the U.K., where it was a bestseller and was named the 2023 Waterstones Book of the Year. Knopf Books for Young Readers will release it in the U.S. on September 10. Impossible Creatures introduces the Archipelago, a secret island chain where fantastical beings are in danger of extinction. Rundell embraced the challenge of building a fantasy world from the ground up while maintaining her economy of language. “I love the idea of a book that can be eaten in a bite, because then I feel that it gets a stronger grip on your ankle,” she says. “But with fantasy, you cannot just say, ‘Imagine Paris.’ When you are inventing something utterly new, you have to lay it out with far more clarity and care.”

Describing her early draft, she says, “I needed to cut it back. I wanted just enough so it would paint vivid pictures for the reader, but also leave space for them to paint in the margins. It’s a thing that I love about all forms of fiction: the participatory power of reading and writing. A book is not really finished when it’s written. It’s whole when it’s read.” Children’s literature produces an especially intimate alchemy between author and reader, she finds: “You give a child a house and they make it into a castle as they read.”

Impossible Creatures has earned comparisons to some of Rundell’s literary heroes: Le Guin, Lewis, Pullman, Tolkien, and others. The challenge of writing in this genre is “making sure that when it’s real, it’s the kind of real I want it to be,” she says. “I want it to be a fantastical world with bite, but with staggering beauty. I spend a lot of time trying to work out how you make it feel like the griffin is actually in your arms, and the unicorn’s breath is on your face, and the dragon’s claw is against the edge of your palm.”

The U.S. edition features interior art by Ashley Mackenzie and an illustrated bestiary and map by Virginia Allyn, helping to bring Rundell’s vision to life. Praising her team at Knopf, including editor Nancy Siscoe (who has worked with Pullman), Rundell says, “They really know how to publish fantasy, and to see the scale of their ambition and hope for the book has been a real thrill.”

Rundell’s creations are born of both imagination and research. “Sometimes these creatures have come when I haven’t been looking for them, when I’ve been doing other forms of academic work,” she says, noting that when she was in the early stages of writing the novel, she “spent a lot of time looking at medieval bestiaries, which would have mythical creatures painted in the margins, to build up a sense of what humanity has imagined into being.” She asked herself, “Why have we created these mythical beings? What have they offered us? And how can I take that and offer it to the next generation of children?” This past spring, research for book two in the series brought her to Venice, a real-world archipelago with its own enchantments—specifically to a library on San Giorgio Maggiore.

Though Impossible Creatures is Rundell’s debut fantasy series, it feels in keeping with the spirit of wonder that infuses her previous stories for middle graders. “Even if you are writing stark realism,” she notes, “I think there is magic in this age group, because they are at an age at which possibility is at its most colossal. They are still on the brink of becoming the person that they will be, and there is magic inherent there.”

At the core of her novels is a respect for the audacity and intellect of young people. “I wanted to say to children, ‘I think you have been underestimated. I think you have in you a capacity for boldness, and for adventure, and for valiance’—qualities that the world has not always saluted in children,” she says. “I wanted to write about children who do experience fear but who also experience a love that is greater than their fear.”

She believes in the galvanizing power of words. “I want to write books that will offer children bold language,” she explains. “But I also want to offer them a sense that if you have a barrage of language at your disposal, you can use it to create better jokes. And you can use it to articulate your love and your passion in a way that will cut through people’s attention and leave them alert—and perhaps changed.”

She hopes, too, that young readers will be encouraged to return to her books time and again. If they skip over a word they don’t understand at first, “then hopefully they might one day go back and gather that word up and add it to their bundle.”

Rundell cherishes the many marvels in the real world, as well, a theme she explores in Vanishing Treasures: A Bestiary of Extraordinary Endangered Creatures (Doubleday, Nov.), a nonfiction book for adults. It was published in the U.K. in 2022 as The Golden Mole and evolved from a series of essays she began writing in 2018 for the London Review of Books. “In some ways, the book is quite intimately connected with Impossible Creatures, which is the fantastical imagining of the real imperiled glory that we live among,” she says. She offers the book as a call to “share the world with the great parliament of the nonhuman that we do not yet understand,” adding, “The earth demands our attention and our political, active, engaged wonder. We owe the world our astonishment.”

As an author, Rundell aims to cultivate that kind of awe in her young readers. “If we could conjure a generation of children who understand that language is power, and language is a source of delight, akin to that of swimming in the sea in bright sunlight—that it has in it human joy—then I think that we would have created something great,” she says.