Detour by D. B. Reynolds

POWER, those who have it reap great rewards…and pay a great price.
DUTY, the little-known strength behind every vampire lord’s rule.
LOVE, stronger than power, and the true root of all duty.
Vampire Lord Raphael has seen North America’s vampire rulers united, and Europe’s defeated. He and his mate Cynthia have spent years achieving that, fighting everyone else’s battles, along with their own. Now, all they want is a vacation. A getaway to someplace romantic and secluded. No guards, no supplicants, no phones—just the two of them with their deep love and endless desire for each other.
If only they hadn’t taken a quick detour to that particular town. Because they soon discover that vampires are dead, and another is missing. And it’s Raphael’s duty to serve justice to the wronged and vengeance upon the guilty, regardless of his plans.
It turns out there really is no rest for the wicked.