Michelle Obama’s “Becoming” is the best-selling hardcover book of 2018.

The former first lady’s memoir has sold more than 2 million copies in all formats in North America in its first 15 days, according to a statement released Friday by Penguin Random House. Now in its sixth printing, the book has 3.4 million copies in print in the United States and Canada.

In a strong indication of Obama’s popularity around the world, “Becoming” is also the No. 1 seller in Britain, Germany, France, Italy, Holland, Spain, Denmark, Norway, Finland and Greece. The book is being published in 31 languages.

Next week, Obama will take a break from her U.S. book tour to make several stops in Europe. On Monday, she will appear at a sold-out event with writer Chimamanda Ngozi Adichie. She’ll be in Paris and Berlin later in the week.

Obama will return to the United States for an event in Detroit on Dec. 11 with comedian Phoebe Robinson.

Perhaps even more striking than the popularity of “Becoming” has been the extraordinary popularity of its author. Obama’s 10-city U.S. book tour has attracted sold-out crowds across the country, with fans willing to pay hundreds, even thousands of dollars to see her. One VIP seat for Obama’s appearance in Dallas on Dec. 17 is selling for more than $10,000.

The vast majority of book authors speak for free to small crowds in bookstores. Obama’s tour resembles a popular music tour — with rock-star prices to match.

“Michelle Obama,” by Antonia Felix, a collection of photographs of the former first lady, debuted on the Washington Post bestseller list last week.

Ron Charles writes about books for The Washington Post and hosts TotallyHipVideoBookReview.com.