The candid memoir, released in November, quickly became a best-seller and is one of the most popular books of the decade.
"We believe this could be the most successful memoir in history," said Thomas Rabe, the chief executive of Bertelsmann, a parent company of Penguin Random House, according to the Wall Street Journal.
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Obama has sold out arenas on her massive international book tour, where she has been interviewed onstage by Oprah Winfrey, Sarah Jessica Parker, Reese Witherspoon and former Obama senior adviser Valerie Jarrett, among others.
The former first lady surprised 13 women in Tacoma, Washington, with a visit to their small book club on Sunday. Obama talked about how important it is to share what makes them different.
"She really advocates for all of us knowing what our stories are, sharing our stories to connect with and inspire other people," Lestraundra Alfred, of Seattle, who started the book club earlier this year. "And that we're all in the process of becoming and we're all figuring this life thing out and doing the best we can with what we have."
People who couldn't get a seat inside scrambled to catch a glimpse of Obama, including Markas Adams and his daughter.
"It means a lot to my family because she has a positive role model to look at," Adams said. "One day it could be her."
In its first week, "Becoming" sold more than 1.4 million copies, Penguin Random House said in November.
The book had the longest streak at No. 1 for any book since "Fifty Shades of Grey" came out in 2012, according to Amazon.
ABC News contributed to this report.
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