Neal Shusterman's novel Challenger Deep (HarperTeen, 14 years and up) is a swirling, surrealistic look inside the mind of one teen, Caden, who is struggling with mental illness. Chapters narrated by Caden alternate between a bizarre shipboard setting and the world we know, all viewed through the teen's sometimes impenetrable perspective. It's a very personal story for Shusterman, whose son Brendan created the book's artwork while in the depths of his own battles with mental illness.

1. What was the genesis of this book?

NS: I had the title "Challenger Deep" long before I had a story. When my eldest son was in third grade he did an ocean report and I helped him research it. We discovered that Challenger Deep is the deepest place on Earth, and I thought that would be a great title for a book, but didn't have a story to go with the title. Then, when my son was in high school, he began to show signs of mental illness. In the depths of it, when he couldn't tell the difference between what was real and what was in his mind, in a moment of despair, he said to me, "Sometimes it feels like I'm at the bottom of the ocean screaming at the top of my lungs and no one can hear me." That's when I knew what Challenger Deep had to be about. I held on to the idea for six years before I began writing it. I wanted to wait until he was in a much better place — which he is; he's been doing amazingly well for several years now. I didn't want to write a book about mental illness without his permission, and I wanted to involve him in any way that I could, so he could turn that dark time in his life into something positive to help others. The story is not about him — but aspects of what he went through are in the book.

2. What was your writing process like? Did you write each thread (realistic and shipboard) linearly? Or did you alternate, the way we're reading it?

NS: The book was written over a period of three years, and I did jump back and forth between sections. I tried to write as linearly as I could, though — since the book is nonlinear, anything I could do to create order in my own writing process helped. There are really three interwoven sections: Caden in his real life, Caden on the surrealistic ocean voyage, and Caden's observations on life. While writing, I color-coded each chapter as to which of those threads it was in. I even had a separate color to mark the shift into second-person, when Caden loses his ability to differentiate between himself and the rest of the world. Structure was key to making the story work, and I did shift sections around to give balance and to make sure that the narrative flowed. It was like piecing together a puzzle.

3. Some of the shipboard personae have clear counterparts in the real world (Hal, Callie, Carlyle). Some are harder to pin down, or they seem to shift. Did you intend for identity to be seen as fluid (pun intended)?

NS: It was important that I follow the rules of Caden's subjective logic, so the identities are fixed, not fluid. Every major and some minor characters in the hospital have a counterpart on the ship. I felt it important that his own family and friends not be represented on the ship because they are not of the hospital, but of his outside life. Also, the captain does not have a counterpart in the real world for most of the story. He's a mystery until the end. What does become fluid, however, is the line between those worlds. As Caden begins to respond to the medication and improve, he begins to integrate them, and we'll see conversations that started in the hospital end on the ship, or vice-versa.

4. How was it to work with your son on this intensely personal project?

NS: I have to admit I was nervous, because it does open up old wounds. I constantly checked in with Brendan to see how he felt, and he would give me notes on the drafts. Using his artwork was crucial. I wanted others to value his art as our family does, as priceless. The works of art that inspired everything that happened on the ship were created when he was in the depths of an episode, when the only way he could communicate the things in his head was through these stream-of-consciousness drawings. I wanted to find light within the darkness of what he had been through, and turn it around. I wanted him — and readers — to see that there is value even in our worst experiences, and we can use those experiences to bring about positive change in the world, and our own lives.

5. What do you want readers to take away regarding mental illness?

NS: Mental illness is by far the most misunderstood, and stigmatized, of all afflictions. Statistically, one in three families in the U.S. deals with mental illness, and yet it's rarely discussed in the open. It's time for that to change. With Challenger Deep, I wanted to offer a fresh, unflinching perspective, to help people understand, and to submerge readers in the strange, surreal depths of mental illness, seeing it from the inside out. Our hope is that empathy and understanding will make all the difference.

From the March 2015 issue of Notes from the Horn Book.