Nicola Yoon had the kind of YA launch that authors dream about. Her novel, Everything, Everything (Delacorte, Sept.), about Madeline, a girl so allergic to nearly everything that she must live inside a carefully sealed environment but finds love through her window in the boy next door, debuted as a #1 New York Times bestseller.

But Yoon traveled a long road before her novel became a bestseller. The idea for Everything, Everything grew out of Yoon’s experience as a new mother caring for her infant daughter. “I started writing when my daughter was four months old,” she says. “I was a super nervous mom and I worried about everything, all the things new moms worry about, like, Are they going to eat dirt? Are they going to crawl out of the house?”

Yoon began to imagine what it would be like if a 17-year-old needed the same level of protection and what her mother would have to be like too. That’s how a story inspired by Yoon’s newborn baby became a YA book. Yoon feels as though YA is a natural fit for her interests. “Young adults are trying to figure out big questions like the meaning of life,” she says. “They’re questioning, and I’m still questioning, too.”

Yoon’s novel contains illustrations by her husband, David, a graphic designer. “I had this idea that my main character would draw as her way of relating to the world,” she says. “I tried to draw the Hawaiian state fish and it was terrible. So I asked him to do it, and it worked so well! We collaborated from there. I’d draw a crappy version of whatever I wanted and then he’d draw the beautiful one that worked.”

As she was drafting the novel, Yoon met Joelle Hobeika of Alloy Entertainment, who would become her agent. “Joelle sent it out on a partial, and we ended up with quite a few people interested,” Yoon says. “Then I interviewed a few editors on the phone. I’d written an outline and wondered which editor would have the same vision as I did. Wendy Loggia was the first person I talked to, and I knew immediately that it would be her! When you know, you know. Wendy was asking the same questions I was, and I thought she would definitely make the book better.”

All told, Yoon worked on the novel for three years. “I had a full-time job when I was writing, so I wrote from four to six a.m.—it was the only time I had,” she says. Yoon, who lives in Los Angeles, worked for a financial firm that kept Wall Street hours. “I had to be at work at six or seven a.m., plus my daughter would wake up at 6:30. I was so tired after three years, my job was so stressful, and all my hair turned gray. It wasn’t sustainable, so something had to give.”

Something finally did—something very happy, for Yoon. “As of May 22 of this year, I was able to quit my job!” she says. “I was able to finally support our little family through the book.” However, Yoon still writes in the wee hours of the morning. She’s gotten used to it by now.

The process of publishing her debut novel has been a wonderful whirlwind for Yoon. “I didn’t even dream this,” she says. “It’s wonderful to have people read the book and have it mean something to them. And the YA community has been wonderful, too.”

Yoon is working on her second novel, but remains tight-lipped about it. “I can’t talk about it yet,” she says. Her daughter, who inspired this turn of events in her mother’s life, is three and a half now, and Yoon is no longer worried about whether she’ll eat dirt. “She can eat whatever she wants,” Yoon says.

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