Obama won the award for the audio version of her memoir Becoming.
The book has now sold more than 10 million copies worldwide.
The hardcover edition of the book sold more copies than any other book published in the United States in 2018, according to NDP BookScan data.
Being published in 31 languages, the memoir is also a bestseller in Australia, Britain, France, Germany, Israel, Korea, Finland, South Africa and Taiwan, among other countries.
Scheduled printing runs mean there will be at least 3.4 million copies of the hardcover edition in print in Canada and United States.
America’s first African American first lady and wife of the first black US president is wildly popular at home and abroad, loved for her warm personality, intelligence and women’s activism.
In the book, she writes that she can “never forgive” Donald Trump for questioning her husband’s US citizenship, accusing him and other “birthers” of putting her family at risk.
She also digs into personal issues, detailing a miscarriage, conceiving her daughters Malia, 20, and Sasha, 17, by in-vitro fertilization and marriage counselling.
While some Democrats would love to see her dive into politics and run for president, she has shot down any suggestion of being interested.
While the precise terms of the book deal were not released, the Financial Times reported that the Obamas were paid more than $65 million for global rights to twin memoirs about their time in the White House.
Barack Obama is already a bestselling author, chalking up “Dreams From My Father” in 2004 and “The Audacity of Hope” in 2008.