The Hot and Cold Book Categories of 2015

It's difficult to overstate the impact adult coloring books had on print sales last year, with the coloring-book craze driving large gains in several categories. The hottest category in 2015 was art/architecture/photography, which had a 60% increase in unit sales in 2015 over 2014 at outlets that report to Nielsen BookScan.

The category was boosted by a number of coloring books, led by Animal Kingdom: Color Me, Draw Me (Lark), which sold 332,000 copies. Two other adult nonfiction segments that had big gains last year were also helped by adult coloring books: crafts/hobbies had a 35% gain in unit sales, with Johanna Basford's Lost Ocean (Penguin) leading. There were fewer coloring books classified in the self-help segment as in crafts, but their presence was enough to help lift unit sales in the self-help category by 15%.

Adult nonfiction had a good year, with a 7% overall increase and only the health/fitness category having a decline in unit sales last year. The 49% jump in the house & home category was due almost entirely to The Life-Changing Magic of Tidying Up, which sold about 1.2 million copies.

In adult fiction, genres in which sales of print books have been damaged the most by e-books continued to show erosion in 2015, as the fantasy and mystery/detective segments each posted 12% declines in unit sales, and romance sales fell 9%. The science fiction genre had a big gain, led by The Martian, which sold just shy of 1.2 million print copies across all editions.

The classics segment got a nice bump from the publication of Harper Lee's Go Set a Watchman, which caused a surge in sales of To Kill a Mockingbird. Paula Hawkins's The Girl on the Train drove an 8% increase in suspense/thrillers, selling 1.3 million print copies.

The juvenile nonfiction category also benefited from adult coloring books, as many titles, including Basford's megapopular Secret Garden and Enchanted Forest, were classified as children's nonfiction books.

Sales of juvenile fiction declined last year, with overall print unit sales down 3% from 2014—perhaps not surprising given the phenomenal year the category had in 2014, when the Divergent series and John Green's The Fault in Our Stars were selling millions of copies. In 2015, the only children's fiction title to hit the million-copy mark was Jeff Kinney's latest Wimpy Kid Book.

Unit Sales by Category, 2014-2015 (in thousands)