Donald Trump’s proudest accomplishment—next to his high-rises, his golf courses, and his daughter Ivanka—is his book, Trump: The Art of the Deal. Published 30 years ago this fall, the book has long served as his calling card—evidence that he’s the greatest negotiator ever to live, and proof positive that he’s fit to be president. When critics tried to laugh him off during his campaign, Trump fired back with his bone fides. “I went to the Wharton School of Finance, I was a great student,” he boasted. “I go out, I make a tremendous fortune. I write a book called The Art of the Deal, the number-one-selling business book of all time.” What else do voters need to know? After all, it’s the rare businessman who can land a spot on the New York Times best-seller list.

Contrary to Trump’s claims, however, other business books have sold far more copies than The Art of the Deal. Total sales figures for Trump’s memoir are estimated at between one million and four million copies—compared to at least seven million for Rich Dad, Poor Dad; 25 million for The 7 Habits of Highly Effective People; and 30 million for How to Win Friends and Influence People. And while it’s true that The Art of the Deal spent 48 weeks on the Times best-seller list—even reaching the number-one spot, where it remained for 13 weeks—that achievement was due not just to Trump’s image as a celebrity, but also to his vanity and penchant for gaming the system.

The story of how Trump all but assured his book reached the best-seller list was first revealed by Jack O’Donnell, a former Trump executive who detailed his boss’s self-dealing in his 1991 tell-all, Trumped! According to O’Donnell, who oversaw marketing and served as president and chief operating officer of the Trump Plaza Hotel and Casino from 1987 to 1990, the Trump Organization helped boost The Art of the Deal by purchasing tens of thousands of copies on its own. In his book, O’Donnell recounts buying 1,000 copies of The Art of the Deal to sell in the Plaza’s gift shop—only to be told by fellow executive Steve Hyde that it wasn’t nearly enough. “You’ve got to increase your order,” Hyde told him. “Donald will go nuts if you don’t order more books.” How many more? Four thousand copies, O’Donnell was told.

“We were pressured to buy a lot of books,” O’Donnell tells the New Republic. So many, in fact, that he had to find creative ways to get rid of them all. “What we would do is use them as a turn-down service in a hotel,” O’Donnell laughs. “You know how in a nice hotel they turn your bedcover down and put a mint there? We were putting books on the bed.”

And it wasn’t just the Plaza Hotel that was buying the book in bulk. According to O’Donnell, Trump executives were instructed to buy thousands of copies for their properties. In typical Trump fashion, the boss pitted his top executives against each other: When Trump’s then-wife, Ivana, ordered 4,000 books for the Trump Castle Casino in Atlantic City, O’Donnell was warned that he needed to match her. “Hey, Jack,” a fellow executive cautioned him, “you better buy as many books as Ivana, or Donald will use it against you.”

At the time Trump was purchasing stacks of his own book, gaming the Times best-seller list was just coming into fashion for desperate writers and publishers. Jacqueline Susann’s Valley of the Dolls, published in 1966, and Wayne Dyer’s Your Erroneous Zones, published in 1976, each benefited from large orders that helped propel them to best-seller status. But Trump helped pioneer the cheating among business authors, who have more resources to rig the system. “Much of this was not very public,” says Laura Miller, a sociologist at Brandeis University who studies the publishing industry. “When you have someone who is the executive of a large organization, there are more financial resources available for large purchases of books—and more of a rationale for doing so.”

The benefits of rigging the system are huge. For authors, being able to tout themselves as a New York Times best-seller can help them land more book deals, TV appearances, and other lucrative gigs. Trump, for his part, parlayed his best-seller status into two new careers: first as host of The Apprentice, and then as leader of the free world. “The New York Times name lends a certain kind of gravitas,” says Miller. “It shows that one is popular among the public, and that this very respected news outlet is certifying that popularity.”

Not long after the success of The Art of the Deal, the Times began taking steps to protect the integrity of its list. In 1995, after business authors Michael Treacy and Fred Wiersema allegedly spent $250,000 purchasing their own books, the Times added a dagger symbol next to books that benefited from large bulk purchases of the kind the Trump Organization was making. But that hasn’t stopped opportunists—especially politicians—from manipulating the numbers. Over the past three decades, Al D’Amato, Scott Brown, Herman Cain, Sarah Palin, and Joe Lieberman have all been busted for using campaign funds to purchase their own books to distribute to donors. In 2015, Ted Cruz got in a lengthy spat with the Times, which refused to place him on its best-seller list after he spent $122,000 on his own book. Even Trump himself returned to the practice he pioneered with The Art of the Deal. Last year, The Daily Beast reported that Trump had illegally spent $55,000 of his campaign funds on thousands of copies of his new manifesto, Crippled America—an initial boost that helped it gain a spot on the Times chart as well, where it stayed for three months.

Even without Trump’s manipulation, The Art of the Deal would have become a best-seller. Demand ultimately proved to be so high that Random House, the book’s publisher, had trouble keeping bookstores stocked with copies. But Trump’s bulk purchases generated much-needed buzz at a crucial moment—and, like so much else he does, served to stroke his ego. While his hotel staffs were hustling to give away all the unsold copies of The Art of Deal he had purchased, Trump insisted on setting up a table in Trump Tower to personally autograph the book for guests. “He loved doing it,” recalls Tony Schwartz, the book’s co-author. Even as The Art of the Deal was garnering the stamp of approval from a publication he now derides as “fake news,” Trump wanted to experience the adulation firsthand.