Hi everyone. I have been calling my finished-but-for-a-few0-more-edits manuscript an historical romance. But it has a really strong mystery element, and after a few additions and tweaks (and after speaking with a freelance editor friend who looked it over) we decided that it really is a mystery with a heavy side of romance. It is set in Victorian England. So, would I classify this as an historical mystery, a romantic mystery, a gothic romance? I don't know why this is so hard, but I just can't figure it out.
Which is central, the romance or the mystery? If you can't figure that out, I suggest reading a couple of books that also mix the two and see if that helps.
Such as: Anne Perry's
The Cater Street Hangman, a historical mystery where two characters fall in love. The mystery is central, but the love story is an important element.
and
Amanda Quick's
Ravished (or almost any of her older ones--haven't read her in years so I'm not sure she's still writing the same type of book), a historical romance which contains a mystery that the couple falling in love is trying to solve. The love story is central, but the mystery is an important element.
It would be hard to produce a gothic romance by accident (mostly because they have a very specific tone), but without knowing more about your story it's hard to say.
If you still can't decide, romance might be easier to break into than mystery, because it commands such a large share of the market.