Radiant Vows: A Dark Vampire Romantasy (Unchained Duet) by Jen Stevens

Her name was stolen. Her fate was sealed. Her rage is just beginning. Kallista Marcellane is chosen by lottery—a vampire bride for the Radiant King in exchange for peace between species. But the lottery was rigged, the peace is a lie, and her own people traded her life for time. Delivered to a palace that glows with weaponized sunlight, she's also dying from the Crimson Blight, a vampire illness manufactured by the very crown she's meant to unite with. The king isn't her biggest problem. General Zevrin Vexrath—the King’s brother and most lethal weapon—is ordered to keep her in line. Their loathing is instant, and so is the heat beneath it. As Kallista fights to survive in a court that sees her as prey, she uncovers secrets the crown tried to bury: letters in the walls, a demon beneath the throne, and a truth about Zevrin that could shatter everything. The winter solstice is coming, and with it brings a ritual that will steal what’s left of her power. She didn't choose this destiny, she was sold into it, and now she's going to burn it all down. Read more