According to 2017 estimates released this summer by the Association of American PublishersThe national trade association of the American book publishing industry; AAP has more than 300 members, including most of the major commercial publishers in the United States, as well as smaller and non-profit publishers, university presses and scholarly societies, sales of adult fiction fell 16% between 2013 and 2017, from $5.21 billion to $4.38 billion. The numbers, though not a major worry, raise questions about the books the industry is publishing and what consumers want to read.