Paper books surge; e-books stall

With items as diverse as an adult coloring books and a new novel by Harper Lee, it was a year for unexpected hits and hits that sold well in paper editions.

As e-book sales remain stalled at about 25 percent of the market, hardcovers and paperbacks held steady at a time digital has upended the music, film and television industries. According to Nielsen BookScan, which tracks around 85 percent of the print market, sales of paper editions increased modestly in 2015. As of early December, 571 million units had sold, compared to 559 million in 2014.

Coloring books for grown-ups, a concept once as unusual as, say, a second of work of fiction from Lee, were the hottest trend. Led by Johanna Basford's Lost Ocean and Enchanted Forest, the phenomenon understandably caught on almost exclusively in the print format, and Basford has no desire to change that. Numerous apps have been designed for adult coloring, but Basford wants her work "experienced only on paper," said Patrick Nolan, Penguin Books' publisher.