These Immortal Vows: A Vampire Romantasy of Power, Temptation & Fate (Bound by Blood) by Kelsey McKnight

Familiars serve. Vampires command. But hearts never obey. Cassandra Rollins was born to serve the immortal. A human familiar bound to the will of vampires, she’s spent her life walking the razor’s edge between power and peril. No creature—living or undead—has ever shaken her control. Until him. Ruairidh Calder, a Scottish vampire forged in battle and haunted by centuries of war, is ready to abandon his wandering life. But when he settles in New York’s glittering vampire court, he’s forced to rely on Cassandra—his reluctant guide and the one human who defies him at every turn. Their fiery clash ignites a forbidden desire neither can contain. Yet when vampires and their human familiars begin to vanish, their uneasy partnership turns into a fight for survival. In a city pulsing with dark magic and ancient rivalries, Cassandra must decide whether to trust the immortal who tempts her heart—or risk losing everything to the darkness hunting them both. Read more