I do think far too many authors struggle with this. Writer's Digest re-tweeted an article I did with them on understanding Women's Fiction and one author Tweeted me directly wondering how an author would classify his or her work if it fell into both categories.
It is important to realize that many genres have sub-categories. For example, we have romantic suspense, historical romance, YA fantasy and so forth. This does not mean, however that the story will be marketed as both of the genres. The book sellers will look to the major force within the story and use that as the basis. What I told the author was the same thing. Look to the main story arc.
If you look at your current story and try to figure out how you would market it, focus in on the one story arc that runs through the entire story. It is that simple. For example, is the central focus:
- the relationship toward the happily ever after? Then it is a romance!
- the understanding of what it is to be a mother in the hectic modern world? Then it is probably a women's fiction.
- the in depth study of a historical couple from European history? Then it is a historical.