The president's vampire
(Book)

For 140 years, Nathaniel Cade has been the President's Vampire, sworn to protect and serve his country. Cade's existence is the most closely guarded of White House secrets, a superhuman covert agent who is the last line of defense against nightmare scenarios that ordinary citizens can only dream of. When a new outbreak of an ancient evil--one that Cade has seen before--comes to light, Cade and his human handler, Zach Barrows, must track down its source. To "protect and serve" often means settling old scores and confronting new betrayals--as only a centuries-old predator can.