I once published an article under my byline that a ghostwriting client read. “I really liked it,” she said, “but it didn’t sound like you at all.” No, I thought. It didn’t sound like you at all!

Because I have collaborated on a dozen books, I carry a lot of voices in my head. Many people believe ghostwriting is stenography. The “author” talks, the ghostwriter types, and voila! A book is born.

That’s not how it works. In the best collaborations, the client opens up about failure and answers the most personal and mundane questions, like, “What office equipment did you use in 1973?” They inherently understand that it might take being asked something multiple times to get to the nub.

But a good ghostwriter has to be ready for the unpredictable. Taking on a book project is like buying a house without an inspection: you know you’ll later discover a faulty wire, a leaky pipe, or a damp patch in the basement—you just don’t know which it will be, or at what point.

When I signed on to my most recent ghosting gig, Up Close and All In: Life Lessons from a Wall Street Warrior, a memoir with former Morgan Stanley CEO John Mack, I braced myself for him to be, well, scary. The nickname he earned during 40-plus years on Wall Street was Mack the Knife, and I was the fourth ghostwriter he had hired for this project.

The unexpected element surfaced on the day we began. I suggested a plan of action, and his response caught me off guard. “You’re the expert,” he said in his North Carolina twang that reminds me of a banjo. “I’m in your hands.”

The man who hung up on the U.S. Treasury secretary, the Federal Reserve chief, and the president of the New York Federal Reserve during the 2008 financial crisis clearly knew what he knew—and knew what he didn’t know. Banking was his bailiwick. Writing was mine.

For me, interviewing clients is just the start. I internalize their voice, how they talk, and the words they use. I immersed myself in John’s world to put readers on the trading floor, in board meetings, and at conference tables with powerful clients around the globe. I don’t have a background in finance, and because Up Close and All In was aimed at a general readership, not just at Wall Street veterans, this gave me an edge. I described the financial realm with fascinated eyes. My daily reading became the Financial Times, the Wall Street Journal, and Bloomberg, and I acquired a library of business tomes.

Besides talking extensively to John and Christy, his wife of 50 years, I conducted 95 interviews. John’s cousins told the story of his mother. Born in Lebanon and a dynamic entrepreneur, she made the same remark every time she stood over the stove stirring a pot: “Best I ever cooked.” The flight attendant who flew with him during the financial crisis recounted how John, usually a gregarious gin rummy fiend, declined to play cards on one trip, instead withdrawing into himself. Former Duke men’s basketball coach Mike Krzyzewski pointed me to John’s interest in military history. I walked around Manhattan, past Morgan Stanley’s headquarters, past the apartment building where John lived in 1968. I flew with John and Christy to Mooresville, N.C., to see his childhood home.

For me, interviewing clients is just the start. I internalize their voice, how they talk, and the words they use.

All of this led to a successful partnership. We finished on time, the book made the Wall Street Journal bestseller list, and the reviews were uniformly outstanding, including one from this magazine. We also became friends and continue to chat often.

Across my ghosting career, I’ve found that most people are too busy to pause and figure out the themes of their lives. It’s my job to capture the complexities and nuances of human experience in a way that rings true to the subject and the reader.

I love what I do. Ghostwriting allows me to live multiple lives. I have adopted the personae of professional athletes, politicians, a first lady, the wrongly incarcerated, statesmen, entrepreneurs, conservationists, and financial titans. I relish the intellectual challenge of taking someone’s story, laying down the foundation, constructing the scaffolding of the themes, and burnishing the narrative with telling details and suspense.

I started out in journalism. One frustration in that field is that you never have enough time to break through the surface because you have to move on to the next article. Working with someone for a year, seeing the elementary school playground where they got into a fight, visiting the ice cream shop they worked in as a teenager—it all allows me to go deeper, to truly grasp who my client is and to capture the mark they’ve made on the world.

This makes what I do a privilege.

Linda Kulman is a bestselling ghostwriter and author.