The former first lady has been touring the country to sold-out venues in support of Becoming, a candid account of her life, marriage to former President Barack Obama and their family's time in the White House

Michelle Obama's Becoming, with 10 Million Copies Sold, Could Be the Most Popular Memoir Ever, Publisher Says

Michelle Obama‘s Becoming has been selling astonishingly well since its November release and, reportedly with nearly 10 million copies now sold, appears to be one of the most popular memoirs in history — if not the most popular, period.

“We believe this could be the most successful memoir in history,” Thomas Rabe, head of one of Penguin Random House’s parent companies, said Tuesday according to the Wall Street Journal.

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Penguin’s chief executive, Markus Dohle, echoed that, the Journal reports. “I’m not aware, in my personal experience with Penguin Random House, that we ever sold 10 million units of a memoir,” Dohle said.

He noted that comparable figures to other memoirs were not immediately available. (Global book sales are not comprehensively tracked.)

For comparison, according to the BBC, citing Nielsen, Becoming is the UK’s 11th bestselling memoir. According to the Washington Post, Mrs. Obama’s memoir sold two million copies in its first 15 days in stores and was a No. 1 seller in Germany, Greece, the UK and elsewhere.

Image zoom Michelle Obama Jim Bennett/Getty

The former first lady, 55, has been touring the country to sold-out venues in support of Becoming, a candid account of her life, marriage to former President Barack Obama, the journey to conceiving daughters Malia and Sasha and family’s time in the White House.

In an at-home interview with PEOPLE, Mrs. Obama talked about the value of being so open — and about her and her husband seeking counseling for their relationship, revered by so many.

“Because we’re role models, it’s important for us to be honest and say, ‘If you’re in a marriage and there are times you want to leave, that’s normal,’ because I felt that way,” she said.

In 2017, she and her husband signed on to publish books with Penguin Random House’s Crown Publishing.