Like all her books Singh has a gift for world building. The places her characters go are very different from the places we inhabit, but they seem so familiar so real. In Angels' Blood Elena is a hunter which means she hunts rogue vampires for the Guild. Vampires in Singh's universe are made by Arch Angels as immortal servants/pets/etc. When Elena is hired by Arch Angel Raphael it's to hunt a rogue Arch Angel.