Writing a book is an act of self-revelation, whether or not you mean it to be, and then once the thing is published you face a second act: self-explanation. Inevitably the question will be asked, “Why did you write this book?” Your response—to an interviewer or a friend—may be the factor that propels readers into your metaphorical arms... or into the arms of another. And there are so many others.

For an author, of fiction or nonfiction, the response seems so obvious, because you have already spent two or more years composing it: “Well, as I say in my book...”

But that is not the answer that those who ask—who, theoretically anyway, have already read your book—are searching for. No, they want something more: the story behind the story; the secret. I have three suggestions that may be of help in giving them what they want.

First, offer up some morsel of your personal narrative that seems to reveal an impetus for sitting down and writing—not so much about the idea you have expressed or story you have told. Tolstoy, remember, described art as the “handing on” of emotions the author has “lived through.” As part of the research for my recent book, Breaking Out: How to Build Influence in a World of Competing Ideas, I had a conversation with Mireille Guiliano, author of the bestseller French Women Don’t Get Fat. The book is sprinkled with moments in which her idea—that joie de vivre is the key to health—is revealed through turning points in her life. The most memorable of these is her return to her native France after spending her senior high school year in America—during which she gained 20 pounds—and her father, on greeting her, exclaimed that his daughter looked like “un sac de patates” (translation: “fat”).

Yes, but many young women struggle with weight and don’t write bestsellers about their experiences. Why did you write this book? Guiliano talked about growing up in a village in northeastern France, a predominantly Catholic country, with a Protestant mother and a nonpracticing Catholic father. “We were really discriminated against,” Guiliano said.

Aha! This author—who, at age 60-something, is now slender and fit—has not only lived through the trials of being overweight but also knows the feelings of otherness that can go along with it.

Second, connect your idea to a practice—a real thing that people do, or can do, themselves. Daniel Kahneman, Nobel Prize–winning psychologist, wrote the bestseller Thinking Fast and Slow. Since we cannot really see or control the two thinking styles the he describes (intuitive and reflective), Kahneman takes to the pages of Harvard Business Review (with coauthors Dan Lovallo and Olivier Sibony) to explain how we can recognize our mental habits and manage our brains better, specifically when it comes to making important business decisions. He formulates his ideas into 12 questions to ask yourself as you deliberate. If you connect the theoretical to the practical in this way, part of the answer to the “why did you write this book” question can be, “I wanted to improve something that needed improving.”

My third suggestion is to connect the idea that underlies your book to other ideas that readers may already know about, understand, or find compelling.

In my research, I talked with Cesar Millan, the famous “dog whisperer.” He is the author of several bestselling books and a star of TV and stage events. I asked Millan if he had any models for his work. His answer, “Gandhi,” came as a surprise to me. Millan quoted the mahatma: “The greatness of a nation and its moral progress can be judged by the way its animals are treated.” Millan’s approach with dogs is to practice “calm assertiveness”; Gandhi advocated “truth firmness” when dealing with humans. Both reject violence. The ideas connect through a long thinking journey, from Buddha through Tolstoy and Martin Luther King Jr. to Cesar Millan. With that answer, Millan put a very different frame around the “why” of his work. I saw a man on a mission much larger than dog training.

This all sounds rather easy, but I have watched many authors struggle mightily to explain why they wrote their books, and I have felt the same heat myself. Sometimes it’s tempting to reply, perhaps a little testily, that it is impossible to know why you wrote the book, or why, for that matter, anybody does anything. That probably won’t get you anywhere.

You need not offer the perfect reason, or even the “real” one. But just trying to answer the question—with an anecdote, a how-to, or a cosmic link—will draw readers in.

John Butman is the author of Breaking Out: How to Build Influence in a World of Competing Ideas (Harvard Business Review Press). He advises and collaborates with individual content experts and leaders of global companies, nonprofit institutions, consultancies, and government organizations, helping them shape and express their ideas and establish idea platforms.