A Crown Without Mercy by J.L. Weir

Nosferatu Lords, Riordan, Nicolai, and Kieran Acheron rein over the Kingdom of Kroyidia, whose future hangs in the balance when Faye and Lycan warriors join forces and prepare to launch an invasion. Although the future of their Kingdom is uncertain, the brothers will stop at nothing to uncover the true identity of a potential mate, being driven by the fierce tides of their destinies.
Unworldly and innocent, Sylvana Orfaedo becomes tormented by thoughts of betraying her family when she looks past the Acheron’s brutal reputations and finds herself unwittingly drawn to them. However, all of their lives are threatened when unanswered questions regarding her mother’s disappearance, the betrayal she never saw coming, as well as the suspicions of dissonance against the crown surrounding her father, unleashes a chain of events that leaves Nosferatu, Faye, and Lycan battling for supremacy. All the while Sylvana faces the greatest threat of all; watching those she loves most become the next casualty of war.