I am a big fan of alternate history books and urban fantasy. Alicia Ryan has done a more than adequate job of blending the two into a fun book. The First Vampire is a story based on the Biblical Samson and his seductress/destroyer Delilah. Ryan weaves urban fantasy into the culmination of a millennia long search by Samson to have his final revenge.
The First Vampire takes elements of alternate history to explain how vampirism came to be through a fluke event.