Lesser Dead by Christopher Buehlman

New York City in 1978 is a dirty, dangerous place to live. And die. Joey Peacock has spent the last forty years as an adolescent vampire, perfecting his routine: feeding by night and sleeping by day with others of his kind in the macabre labyrinth under the city's sidewalks. Until one night he sees them hunting on his beloved subway. Vampires, like him... or not like him. Whatever they are, whatever their appearance means, the undead in the tunnels of Manhattan are not as safe as they once were. And neither are the rest of us.