Unholy Embrace vampire novel by Neil Benson -loving a vampire

Frank, a mortal, thinks heavily on an emotional commitment to his girlfriend, a vampire.

After leaving her apartment, I was walking toward Central Park within five minutes. If I took too long to decide, our relationship would end. Nessa had been lonely for over four hundred years. She made a choice about me, perhaps impulsively, but now I knew how much I meant to her. She would be devastated if I rejected her, and I had no wish to be the cause of such pain. But I also needed to consider the risks involved.

I walked along the outside of the park until I found myself in front of the Museum of Natural History. For all the information it contained, it didn't have displays about creatures the visitors were better off not knowing. Nessa, werewolves, and demons didn't exist in any of the museum's catalogs. However, she was also a woman, one that aroused the strongest feelings I had ever experienced. Should I make a commitment based mostly on feelings? I was always so rational. To go with her was to step into the unknown and far beyond my comfort zone.

When I looked at my watch, I saw five hours remained until dawn. For once in my life I decided to go where my heart led. I walked south until I hailed a cab, and in a few minutes I was back at her apartment. The strong need I felt to be with her contrasted with how I felt two hours ago. Time is not measured in minutes or hours but by the manner in which we experience our lives. When I stood in front of her door, I knew my decision.

http://www.amazon.com/Unholy-Embrace-Neil-Benson/dp/0982679505/ref=sr_1_2?ie=UTF8&s=books&qid=1274835629&sr=1-2