Combined print book and e-book sales hit 942 million units in 2020 at outlets that report to NPD BookScan (for the US market), a 9% increase over 2019 and the most unit sales recorded in a single year by BookScan since the service was created in 2004. In a webinar held last week, Kristen McLean, executive director of NPD Books, said the gain was due to a combination of strong sales of both print and digital books.