Besides the old TV series Dark Shadows and a dumbed-down kid's version of Dracula, this book was the only real early introduction to the vampire myth I had (later on, when I was inspired to write my own vampire novel after reading an article in Christianity Today about the Christian roots of the "horror" theme in literature and movies, I didn't read other works in the subgenre, so as not to be unduly influenced, until my own book was finished). I read this one as a young teen, and it's well-written enough to have left a lively impression after all these years --though I was only recently able to identify the author and title again, through some good help from the Goodreads Vampire Lovers group.
Whitten noted that he wrote the book to explore the question of how a modern urban police department (it's set in Washington, DC) would cope with an actual vampire; so it's a blend of vampire novel and police procedural, as the cops try to find the killer of a young prostitute, and gradually find mounting evidence that the perp is a vampire --though they resist that conclusion. (The supernatural aspect is artfully handled; they never find conclusive proof that the villain is really one of the Undead --but they don't prove that he isn't, either, and there was definitely no doubt in this reader's mind about what he was!) Despite the victim's occupation, I don't recall that the book actually had any heavy erotic content (unlike some later vampire fiction), nor do I recall any major amount of bad language or gratuitous gory violence; that kind of thing would have turned me off markedly, back then as well as now, if it had been present. I do recall that the male-female pair of officers investigating the case came across as likable, and that the plot held my interest from start to finish.