Unit sales of print books rose 1.3% in 2018 over 2017 at outlets that report to NPD BookScan. According to BookScan, which tracks 80% to 85% of print sales, units topped 695 million in the 52-week period ended December 29 compared to 686.9 million in 2017. Print book sales have been trending upward, albeit at a slow pace, since 2013.

The modest 2018 gain was driven by the adult nonfiction segment. Not only did political books pile up big sales last year, but Michelle Obama’s Becoming was 2018’s runaway bestseller, selling 3.4 million copies at outlets that report to BookScan.

A total of five books sold more than 1 million print copies in 2018, all of which were frontlist titles. In 2017, the two top selling books were backlist titles, Wonder by R.J. Palacio and Milk and Honey by Rupi Kaur.

The only other segments that posted unit gains in the year were juvenile nonfiction, where copies sold rose 3.0%, and young adult nonfiction, where units were up 8.5%.

Unit sales of adult fiction fell 4.6% in the year after falling a much more modest 0.7% in 2017 compared to 2016. Juvenile fiction sales dipped 0.9% in the year and young adult fiction sales declined 0.1%.

By format, hardcover was the big winner in 2018, with units up 6.2%. Sales of board books rose 2.3% over 2017, but sales in the other print formats fell in the year.

Physical audiobooks had the steepest drop, with units off 28.9%. Trade paperback unit sales, after rising 1.5% in 2017 over 2016, slipped 0.5% in 2018. Unit sales of mass market paperback dropped 6.1% in 2018, only slightly slower than the 6.4% decline reported in 2017 compared to 2016.