Photo by Tsar Fedorsky/Getty Images for Reed Business.

Marcelo is a bright 17-year-old who works with therapy horses, is wild about religion, and stumbles humorously into his first romantic relationship. You once lived at a home that was part of L’Arche, a faith-based community in which so-called normal adults live alongside those with developmental disabilities. What did you learn from that experience?
When you live with the disabled, you learn more from them than, frankly, they learn from you. The people who are so-called disabled have a true place in our world and actually contribute to healing some of the things that are wrong in our society. What I took away from L’Arche was a sense of the vulnerability, the purity that these folks have, which is something that’s missing in the modern world.

Marcelo has Asperger’s syndrome, which makes it hard for him to respond to common social cues. What’s your take on him?
Marcelo is perfectly happy listening to both real music and something that he calls internal music, for lack of a better word. He’s content on his own. He’s not missing out on friendships, but he’s a little bit of a hermit. He goes to a special school. He’s beloved at home. I would characterize his view of looking at the world as “before the fall.”

What do you mean by that?
He’s not acquainted with suffering. Or if he is, it just hasn’t hit him. At the beginning of the book, Marcelo’s mother is trying to convince him to work at his father’s law firm for the summer—to work in the “real world.” She’s an oncology nurse, and she’s wondering whether she made the right decision, many years ago, in taking him on Saturdays to play with the kids in her hospital. And Marcelo says, “Suffering and death don’t affect me the way they do other people.” That view, which in some ways is a saint’s view, gets transformed as he becomes more acquainted with the real world.

I usually can’t stand novels that involve religion, but you write about spirituality in such an appealing way. What’s your secret?
Well, character comes first. I first created the character of Marcelo and then found out what might be a diagnosis for what he had—as opposed to starting off with a disability that I wanted to create a character out of. Also, I cheated a little bit because I have a character whose prevailing interest is religion. The other thing that is unusual about Marcelo is he’s not tied to one denomination. He visits a rabbi. He repeats a Shin Buddhist prayer. He goes to mass with his father. He goes beyond dogma. When he has this little crisis of faith, he goes to the heart of the matter for all of us, asking, Why is there suffering? What does it mean to have knowledge of good and evil?

One of my favorite novels, Franny and Zooey, explores those same mysteries.
I’ve reread Salinger’s books. All of them are kind of amazing, don’t you think? Franny and Zooey and then the short stories and Seymour.

They all feature characters who are struggling to live compassionate lives, who are trying to be, in a way, holy. I think your book is part of that lineage.
Boy, that’s quite a comparison. I can go home happy now.