Michelle Obama's book 'most valuable' of 2018
Michelle Obama's memoir Becoming was the "most valuable" title of the year, according to The Bookseller.
The book, which came out before Christmas, topped bestseller charts and brought in £7.7m in sales.
It wasn't the best-selling book of the year, but its release came at an important time, says the publishing magazine's editor Phil Jones.
"Traditionally, Christmas has been a time for deep discounting of books," Jones told the BBC.
"Led by supermarkets and Amazon, those discounts particularly focused on the big celebrity titles, where discounts might typically be more than 50% off the recommended price (the price set by the publisher)."
But with Becoming, he said this didn't happen as much and the book was mostly sold for near to its £25 set price.
The book, which explores Obama's experience from childhood, her work, motherhood and her time in The White House, was praised for its universal appeal across genders and ages.
"It's a sign that it stood out as a title and that readers (or gifters) were prepared to pay for the package," Jones added.
"The number of copies it sold (boosted by her sell-out appearance at the South Bank) combined with its cost meant it was the most valuable book of the year - a triumph for all concerned."
Nielsen BookScan monitors UK book sales and says 190.9 million books were sold last year, creating a total revenue of £1.63bn.
This was an increase on the amount of books sold in 2017, with an extra 627,000 sold.
The biggest title was Gail Honeyman's debut novel, Eleanor Oliphant is Completely Fine, while Adam Kay's This Is Going To Hurt: Secret Diaries of a Junior Doctor, topped the non-fiction sales list.