A new book is laying claim to be the most sexual ever written (on the basis that publishing on Kindle breaks the shackles that normal publishers would apply).
But it's fundamentally a romance book, the sex is just part of the romance:
- The male narrator almost always falls in love with the women he has sex with
- The whole book holds together because of his love for the central woman character Willow.
- Generally there is a reasonable balance of power between women and men.
- Although the sex is explicit, women are not treated as objects.
I think that if a book has these things, it's a romance book.