The question I get asked most, when people find out what I do, is: why children’s books? Why not write proper books, for adults?

My answer will depend on the day. Sometimes, in a bad mood, I say, “Well, they’re a lot shorter.” Sometimes I tell the truth: children are extraordinary readers. One of my favorite things about meeting young readers is that sometimes they describe to me, in great detail, a scene from my book that I never wrote. It happens surprisingly often: a kid will love the ballroom-dancing scene on the Paris rooftops [in Rooftoppers], or the moment in Cartwheeling in Thunderstorms when Will jumps from the back of one horse to another. Those scenes don’t exist — except, now they do. Children, as they read, paint with bright colors in the margins fiction leaves open. Their imaginations are so bold and tumultuous that they build on the world when they rethink their books in memory. I was startled myself, when I reread some of my favorites as an adult, to see how many of the details I knew by heart never appeared. Lucy Pevensie never spins in the snow, and Peter Pan never flies through a thunderstorm; I had imagined them. Children read the world into largeness. When you write, you build them a house, and when they read, they make it into a castle.

There is another reason, though, why I love children’s fiction so hugely, and I’m taking advantage of the fact that I’m not reading these words myself to talk about something more personal than I usually do. (I’m British; we are usually most comfortable when talking about weather or whether it’s acceptable to put milk in Earl Grey tea.) I come back to children’s books because children’s books came for me when I needed them most.

In the years I was nine and ten, my teenage sister grew gradually more ill until she fell into a coma. For two years, I read my way through long periods of being alone, in hospital waiting rooms and car journeys and friends’ houses. The books I read then have stayed with me, under my skin, ever since. We say, when people die, that they have lost the battle against illness, but the children’s books I read in those two years taught me something life-changing: in one important way, my sister didn’t lose; she won. To fight with such patience and love is to win. She was brave to the very end, and she is the reason my three novels are peopled with girls who fight bravely, without always winning in the obvious ways.

It is difficult to know what to say to a child who has experienced loss, and a lot of adults resort, understandably, to sentimentality. But the books I loved were without sentiment; they were sharp and fierce and witty. At age ten I found myself lost, and they — Matilda and Pippi and Harry, Claudia Kincaid and Will Stanton, the Fossil sisters, and Wilbur the pig — helped me up and led me home. The value of children’s literature cannot, of course, be predicated on pain — books are not only valuable when we have something to escape from — but in fact those books were not an escape. They said: look, this is what bravery looks like. This is what hope looks like. They told me, through the medium of wizards and lions and babysitters and talking spiders, that this world we live in is a world of people who tell jokes and work and endure. Children’s books say: the world is huge. They say: hope counts for something. They say: bravery will matter, wit will matter, empathy will matter, love will matter.

Although it is published as my second book in America, Cartwheeling in Thunderstorms is the first thing I ever wrote, which makes me doubly thrilled that it was chosen for this prize, because Cartwheeling was the book in which I came face-to-face with all the joy and difficulty of writing for children. I wrote Cartwheeling in Thunderstorms in a whirl of late nights in a single month, when I was twenty-one (which, incidentally, has led me to consistently underestimate the time it actually takes me to write a book — about a year and a half — for which I apologize most sincerely to my editors). I had never tried to write anything of any length before; essays at university had been two thousand words. But I had a story, loosely based on my own childhood, that I wanted to tell, and I knew I wanted to try to write the dusty sun and huge skies of Zimbabwe back into my life. I tried to write just over a thousand words a day, every day. If things got truly desperate and my willpower abandoned me, I would tie myself to my chair with a skipping rope and not untie it until the words were done. I am pretty sure Shakespeare did the same thing.

Cartwheeling in Thunderstorms, then, will always be the book I hold very close to my heart. But it seems unfair to me that it is only the writer who gets her name on the front cover, instead of a page of credits, like in movies. No book is built by a single mind, and I owe so many thanks to so many, many people. The [British] editor of Cartwheeling, Julia Heydon-Wells, was remarkable. Looking back, I was a clueless twenty-one-year-old who knew nothing about editing or marketing or anything, really, except what it was like to ride through the Zimbabwean bush. I will always be grateful to her and to [publisher] Faber for taking a chance on me. I also have a spectacular agent, Claire Wilson, who is a champion and hero and friend, and who found me a home at Simon & Schuster, which has been a gorgeous and welcoming place. Finally, by asking David Gale to read this out, I’m making him thank himself, which is a particular pleasure because he is so modest and so brilliant. He is known in England amongst writers for the sharpness of his vision and the unswerving excellence of his taste. Being chosen by David for his list was the closest I have ever felt to getting into Hogwarts. Most of all, I am grateful today to the Boston Globe–Horn Book Award judges. Awards like this shine light on children’s books, and I am so thrilled to be part of that world. For thousands and thousands of children like I was at age ten, children’s books are not a way out but a way back in. Adventure stories and school stories, fantasy and science fiction and classics: they weren’t a crutch; they were wings.

From the January/February 2016 issue of The Horn Book Magazine. For more on the 2015 Boston Globe-Horn Book Awards, click on the tag BGHB15.