All good business stories begin with an economist admitting he has no idea what’s going on.

“I just don’t get it,” Richard Thaler told me a few months ago, when I asked how his book tour was going. “More people are listening to my book than reading it.”

Thaler is an entertaining writer as academics go, deftly distilling complex ideas. And the subject of his book, “Misbehaving,” is compelling: the psychological quirks and failings that distinguish actual humans from the rational action figures many economists suppose walk the Earth. I had to agree with Thaler, because I didn’t get it either.

Though I’m a heavy audiobook listener, and have written about how the technology is changing our relationships with reading, exercise and time, that audio has grown popular enough to outsell some traditional books is hard to fathom. Audiobooks racked up $1.5 billion in sales last year and remain the fastest-growing segment of the book publishing industry, according to the Audio Publishers Association, but text is still king.

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It turns out Thaler is hardly an outlier. When I called Audible, Amazon’s AMZN, -4.12% audiobook subsidiary, the company crunched the numbers and found examples of books in every imaginable genre that sell better as spoken than written words — sometimes four times as well. (Characteristically reticent Amazon declined to give exact sales figures across formats.)

So why were these audiobooks outselling the text versions? As I studied the range of romance novels, thrillers, self-help and business books that sold better in audio, I could find no discernible pattern or formula to explain what made a title an audiobook hit.

It didn’t make sense.

Then I talked to Andrew Peterson. When his debut novel, “First to Kill,” about a PTSD-rattled former Marine sniper turned covert CIA operative named Nathan McBride, was published, there were no plans for an audiobook. The publisher wasn’t willing to take a chance on producing an audiobook for the first-time author.

Peterson, himself an audiobook listener, decided to use his own money to hire his favorite audiobook narrator to record the thriller: Dick Hill.

Listen: “Ready to Kill,” by Andrew Peterson (on SoundCloud)

“The truth is that whenever I write, I imagine to myself how this will sound with Dick Hill reading it,” Peterson told me. “There’s just something about his voice — he’s truly a world-class narrator, and I knew it had to be him.”

Hiring Hill proved to be a brilliant investment. In his 30-plus years of recording audiobooks, Hill has narrated everything from Mark Twain to Dave Barry, but more recently he’s best known as the voice of Jack Reacher, the hero of Lee Child’s mega-best-selling series. After listening to Hill read the latest Reacher book, obsessive fans wanted to keep listening, so they searched out other books Hill had narrated.

“If you liked Jack Reacher, the main character in this book reminds me of him,” one commenter said on Audible’s site, referring to Peterson’s book. “I have listened to many Dick Hill narrations. In fact, searching by his name is how I discovered Andrew Peterson,” another added.

When I told Hill how his voice propelled Peterson’s series, which were four times as popular in audio as other formats, he said he had had “no idea.” He works for fees, he said, and narrators don’t collect bigger windfalls if the audiobook is a hit.

But based on his fan mail, he said, he is not surprised his voice led Lee Child fans to Andrew Peterson. “Lee Child fans are legion,” he said. “When some of them get turned on by something they need to tell other Lee Child fans about it, and I guess it just grows from there.”

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Amanda Ronconi, who narrated all of Molly Harper’s supernatural romance novels, also said she had been unaware that the audio was selling twice as well as the text — that is, until the author told her she was able to “quit my day job” because of audiobook sales.

The fact that audiobook narrators have developed the followings and star power to drive sales represents a seismic shift in the way books are sold and consumed, said Donald Katz, Audible’s CEO. “This is a completely different phenomenon — a cultural and, frankly, aesthetic change in people’s habits,” Katz said.

It’s also a major reason Audible has been bringing in big-name stars as narrators: Jake Gyllenhaal reading “The Great Gatsby” and Tim Robbins reading “Fahrenheit 451,” for instance.

Not all audiobook hits are attributable to how great or greatly known the narrator is. When Joshua Kaufman’s business book “The Personal MBA” was published, the audiobook outsold the print version three to one, even though Kaufman did the narration himself.

The reason? The rise of audiobooks isn’t just about the quality of the performance but the fact that many readers prefer the experience to text. “For a long time the industry treated audiobooks as a subsidiary format, but now we’re seeing it’s become a primary format for many — and has been for some time,” Kaufman said.

Management guru Peter Drucker said there are two kinds of people in the world: readers and listeners. He was referring to how we learn and process information, but, based on the sales figures for Thaler’s economics book, Peterson’s thrillers and Harper’s romances, he could just as well have been talking about how we consume books.

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