A Vision in Crimson by Kathryn Troy

A hunter without a purpose. A witch out of control.
Together, they will burn.
Katelyn's magic is risky, but she's desperate. Icaryan light is fading. A chance meeting with a half vampire might be her last hope.
The darkly charming Luca is the one person able to stop Kate's spells from swallowing her whole, but is he willing to follow her into a dark, wondrous world, full of magic and mischief at every turn?
Kate and Luca fight side-by-side against assassination plots, long-lost lovers, an illegitimate heir, and a slaver's growing appetite for Icaryan citizens. All the while, Kate's power is growing, its source just out of reach. Pulled in every direction, the dangers they face threaten to tear them apart.
Luca is faced with a terrible choice: turn her with his bite into the thing he hates most, or risk losing her forever.
Torn between fear and desire, he abandons his own futile hunt to find and kill his father-the vampire lord who has never forgotten him.
Perfect for fans of Jennifer L. Armentrout, Carissa Broadbent, and Deborah Harkness, A Vision in Crimson is the first book in this dark romantic fantasy series.