Christopher Golden 
Gathering Dark 
you’ve read game of thrones, now read this

The Gospel of Shadows enabled the Catholic Church to control all manner of supernatural beings for centuries. When the book was destroyed and the ruling body of the Church with it it enabled the Shadows, the vampires of legend, to learn the hidden truth of their triple nature: part human, part demonic, part divine. But it also weakened the barriers that exist between the worlds, and now beings of pure evil are breaking through creatures from other dimensions for which Hell is just a name. Peter Octavian, once a powerful Shadow, now restored to humanity, is the only man with sufficient knowledge to stop them. Aided by an earthwitch, a vampire and a priest, and calling on the magical forces of mother nature herself, Octavian stands between the Earth and apocalypse, as entire cities are plunged into the abyss…