Sweet Ruin by Kresley Cole

Growing up, Josephine didn’t know who or what she was—just that she was an outcast with strange powers. Protecting her baby brother became her entire life. The day he was taken away began Jo’s transition from would-be superhero…to enchanting villain.

Archer Rune the Baneblood never fails to eliminate his target. In his sights: the oldest living Valkyrie. Yet before he strikes, a vampiric creature pierces him with aching pleasure, stealing his forbidden blood—and jeopardizing his brethren’s secrets… Read more.