The former First Lady Michelle Obama's Becoming memoir became the best-selling book in the US 15 days after its release.
According to NPD BookScan, more than two million copies were sold in the US and Canada.
Sales were announced on Friday by Penguin Random House.
The publisher says the book is a bestseller in many other countries, including Australia, Britain, France, Germany, Korea and South Africa.  Video: When Michelle Obama Hugged the Queen
The book is a window into the personal life of the Obama before, during and after her time at the White House first African American First Lady and first black US President Barack Obama.
In it, Ms. Obama reveals difficulties in her marriage to Barack, revealing details of how the couple miscarried and later used in vitro fertilization (IVF) to receive both children, Malia and Sasha.
The 54-year-old also criticizes US President Donald Trump and writes that she can "never forgive him" because he "endangers the safety of my family" from the "birther" theory that her husband was not born in the US and thus was not a legitimate US President.