Let me know where to send it...
This is because of the genre expectations.
In horror, either the big bad or the protagonist has to be defeated in the end.
And despite the many slasher sequels, it’s hard to bring back the big bad in another non-slasher genre.
Romance is even harder. Romance HAS to end with Happily ever after otherwise, it’s not a romance. It’s a love story. (Nicolas Sparks writes love stories.)
So exactly do you turn multiple standalone books into a series?
The Nocturne Falls way.
You see, Nocturne Falls is the name of a fictional town in a series by author Kristen Painter. It’s full of supernaturals pretending to be humans, and it’s Halloween all year round. (my type of place)
Every book takes place in this town and features the supernaturals and sometimes, even some mortals.
But the really clever part is how they continue the series. As the stories unfold, we see bit players who have names; other family members, the shopkeepers, the doctors, the cops. But the clever part is that the bit player in one book becomes the central player in the next book.
One by one, book by book, we watch the characters get married off and have their happily ever after. We see the central players then get turned back into bit players so we can follow parts of their happy life without a separate book.
Then, we get introduced to some new bit players and the stories continue.
It’s a brilliant way to write a series while still staying true to the tropes of romance.
The cozy mystery series shows some bit players we’ve seen in the romance and the manager of one of the stores that keep popping up throughout the series.
This crime-solving supernatural solves mostly supernatural mysteries and disappearances. No one ever dies in Nocturne falls. The cozies have the same fun and quirkiness that the romances have.
In this way, the author was able to write both mysteries and romances and sell them to the same audience without having to build a new one from scratch.
It’s brilliant in its cleverness and it’s something that’s repeatable for the right author with their own series.
Bit Players become main characters and once a fan base is established and a world is built, the series parlays into a separate series in a different genre with all the fun of the original.
Of course, none of this works without great characters and solid world-building, so make sure you put in the time to do that.