Because You're Mine by Kristopher Triana

Bryan’s elderly mother is terminally ill, and that’s the way he likes it. Mom comes from old money, making it easy for Bryan to hire an in-home nurse, but he’s looking for someone to provide a special kind of treatment, something he’s long fantasized about.

Shelby is a nurse with a horrible secret. When she begins caring after Bryan’s mother, the two strike up an unlikely kinship, bonding over their troubled pasts and hidden desires. Together, the older Bryan begins teaching Shelby classic methods of diabolism, and she teaches him about the modern tools of their terrifying trade, making them a duo to die for.

Because You’re Mine is an extreme horror romance from the dark heart of Kristopher Triana, author of Gone to See the River Man and They All Died Screaming.