By Jim Milliot | Jul 09, 2021 photo credit: Logos-Bookstore-Yorkville In the first half of 2020, unit sales of print books surprised many in the industry by posting a 2.9% increase over the same period in 2019 at outlets that report to NPD BookScan, overcoming a slump in sales in early spring following the onset of the Covid-19 pandemic. Print sales finished 2020 up 8.2% over 2019, and that strong performance continued into 2021, with units jumping 18.5% in the first six months over the comparable period in 2020. With the exception of the juvenile nonfiction category, all the major publishing categories had