If the sales of mass-market adult hardcover books accounted for 33 percent of mass-market book sales in 2010, by approximately what percent did the dollar amount of sales of this type of book increase from 2010 to 2015 ?
If the sales of mass-market adult hardcover books accounted for 33 percent of mass-market book sales in 2010, by approximately what percent did the dollar amount of sales of this type of book increase from 2010 to 2015 ?