It's common knowledge in the publishing industry that women constitute the biggest book-buying segment. So, it's certainly no accident that most mainstream as well as genre fiction is popular among women. For that reason, publishers and booksellers have identified a category within the mainstream that they classify as Women's Fiction. And its no surprise that virtually all the selections of Oprah's Book Club are in this genre.
From a writer's perspective, some key characteristics of these books include a focus on relationships, one or more strong female protagonists, women triumphing over unbearable circumstances, and the experiences of women unified in some way.