King of Battle and Blood by Scarlett St. Clair: (paperback english)

Battle and Blood is the first book in the Adrian X Isolde series, blending elements of dark fantasy, romance, and political intrigue. The story follows Isolde de Lara, a princess trained as a warrior, who is forced into an arranged marriage with the vampire king, Adrian Aleksandr Vasiliev, to end a long-standing war. Her mission is to assassinate him, but when her attempt fails, Adrian threatens to raise her as an undead if she tries again. As Isolde navigates the dangerous vampire court, she grapples with her growing attraction to Adrian and the complex dynamics of their relationship.