The Infernal Devices. I literally don't know how I read the majority of the Mortal Instruments books before reading this series. I definitely recommend that every one reads the Infernal Devices before the Mortal Instruments
In Norse mythology, a Valkyrie is one of a host of female figures who decide who will die in battle. Selecting among those who die in battle, the Valkyries bring their chosen to the afterlife hall of the slain, Valhalla, ruled over by the God Odin.