Book publishing revenue increased 5.5% in the January to April period over the same period in 2017, according to figures released by the AAP. The year-to-date gains include a 4.4% sales increase in April, over April 2017.

In the trade segment, sales of adult fiction and nonfiction rose 7.3% in the four-month period and sales in the children's/young adult category rose 6.6%. Sales or religious presses increased 9.8%.

The strongest performing trade format was downloadable audio, where sales jumped 36.1%. Sales of physical audio, however, continued to struggle; they were down 11.4% in the four month period. Hardcover sales rose 11.8% in the period, and trade paperback and mass market paperback sales inched ahead 1.4%. In a bit of a surprise, sales of board books, which had been growing quickly, fell 5.5%.

The decline of e-book sales continued into the early part of 2018 and were down 3.8% among companies that report to the AAP, compared to the first four months of 2017.

The numbers were collected as part of the AAP's StatShot statistics program, which draws information from more than 1,100 publishers.