Companions of the Night by Vivian Vande Velde

"Kerry Nowicki helps a young man escape from three other men who claim he is a vampire and, when her father and little brother are kidnapped, Kerry joins forces--and falls in love with--the accused vampire." (from Amazon.com)

Hardcover Info: ISBN 0152002219, Harcourt Brace, 1995 (Shown)
Paperback Info: ISBN 0152166696, Magic Carpet Books, 2002