Forbidden Wolf by CR Robertson

When two immortal enemies give into their forbidden desires, their passion puts both of their lives on the line.
One a lycan, the other a vampire, Levi and Tasha’s very survival hinges on remaining sworn enemies. But one night changes everything, resulting in a relationship between the two. A relationship punishable by execution should either be caught.
Fueled by hate and inflamed by boundary disputes, their warring species will never accept their love. But just as Levi and Tasha plan their escape, a new danger emerges that threatens both of their worlds.
As the pair discover why their species have really been kept apart all these years, they soon realize their own secret may be the key to unlock the survival of their species. But if their passion is discovered by the wrong people, they might find themselves dead before they get the chance to save anyone.