Where do book ideas come from? That first spark, that moment of conception? If I believed in God, I’d say that book ideas come from Her. Since I don’t, I wonder if they come from an accidental accumulation of living: riding the subway, reading a book, drinking coffee, remembering a moment. Then, wham, book idea.

Four years ago my wife and I got our daughters two kittens. A year later, one of the cats died. On Christmas Day, just like that. Our daughters were devastated.

I grew up on a farm and it seemed our cats, dogs, horses, and goats were always giving birth or dying. Often life was wondrous; sometimes it made no sense. When I was six we had a puppy who was kicked in the head by a horse. She bled in my arms as we drove to the vet and I can recall the heaving of my body when the vet told us there was nothing he could do.

So when I looked at my daughters bent over the body of their cat, I knew what they were going through. I also knew, at some remove, that the arc of their grief would turn for the better. But knowing that and imparting such a life lesson were different things.

All winter and spring I mulled over this. I went for runs around Central Park. Read books. Drank coffee. Watched football. Got a new kitten for my daughters. Went for runs. Read books. Watched my daughters play with the new kitten. Mulled some more.

In the fall I flew to Chicago, where we once lived. As I walked through the door of the café where I used to write, a phrase came to me. As I stood in line, a sentence followed, a circular structure. I sat and opened my notebook and in 10 minutes wrote 20 sentences and sketched a 32-page dummy. One cat, another cat, one cat dies, another takes its place. Our family’s story, simplified. And though no writer, especially one describing the writing process in a Publishers Weekly essay, should be trusted entirely, the idea for my book Big Cat, Little Cat was conceived in minutes, and those minutes remain a mystery to me, and I was there.

If a book’s conception is a mystery, I find its making to be the opposite. At least, the painting of a book. There’s a straightforward physicality to it. Paint, brush, paper. Using one’s hands. Taking an idea and nurturing it, teaching it to walk and talk. The happiness of raising a child, without the confusion.

As with all my books, I had a routine. Each morning I made coffee the same way, painted while listening to the same music, then taped the finished art on the walls above my desk. Each night I showed the paintings to my family as our actual cats made figure-eights around our legs. The following morning, same routine.

I’ve always enjoyed this time. Its intimacy. Watching a book grow into what I imagined it could be, watching it expand and literally take over the room. But this never lasts. Eventually I had to deliver the art uptown to the publisher. A bittersweet moment, like dropping one’s child off at college.

With the art gone, and the process of editing, proof-correcting, cover-designing begun, the book receded. At least, its creation receded. It receded because of time, new projects, new ideas. It receded with advance reviews, which though they pleased the publisher, felt to me like hearing stories about someone I used to know. Even the finished book, which looked beautiful and made me proud—I wanted it to do well in the world—felt a bit foreign to me. One day I saw the book in the hands of a stranger.

I was at Three Lives & Company, my neighborhood bookstore, and I saw a woman reading Big Cat, Little Cat, and she was crying. A few days later I saw two girls reading the book to each other, smiling and pointing out some detail, unknown to me.

My idea, my meditation on my daughters’ grief, the paintings that had covered the walls around my desk, now belonged to someone else. My book was no longer my book, not quite, and knowing this was both sad and right. Humbling. It had become another person’s story, or room, a space in which they could dream or draw comfort. Their mystery.

If I were to finish my own metaphor, though, and close this circle, last week I went uptown to the publisher and picked up my paintings and carried them home on the subway. I brought them back to our apartment, where I placed them in an archival box. Then I put the lid on top of the box and slid it under our bed—joining boxes of paintings of farms and trains and beaches—where it is resting now.