Romance literature, though, has historically contained significant elements of sexual violence. A 1987 review by Carol Thurston revealed that in the 1970s, half of all romance novels included the rape of the heroine, typically by the hero/love interest. Fifty Shades of Gray was by far the top selling book of the 2010s. The second-best-selling book of the decade was its sequel, Fifty Shades Darker. The third best selling-book was the last of the trilogy, Fifty Shades Freed.