The Vampire Detective: The Complete Series
Luckily for Lucy, she doesn't have to solve it alone. Between the support of her long term almost-fiancé, her former best friend turned rival, an oddly behaving blood slave, and an eccentric inventor, she might actually have a chance at solving the puzzle.
As they all find themselves drawn deeper into the dark world surrounding blood slaves and the illegal practices surrounding them, Lucy realises she's going to have to use her family connections to put a stop to things she doesn't agree with.
The Vampire Detective complete series includes Fangs For Nothing, What The Fangs, Fangs For All, and An Origin Tail. It is an urban fantasy series with a polyamorous romance plotline.