Considering that a book can only have one main character, I guess the field you would be looking at would be the other top-ranked books and the racial backgroun

Considering that a book can only have one main character, I guess the field you would be looking at would be the other top-ranked books and the racial background of their main characters. In a similar way that a "diversity hire" doesn't have to be female and black and latinx and LGBTQI and etc - they would just have to be one/some of a similar minority, thereby contributing to the diversity of the workplace/community as a whole.