Changeling: Order of Darkness, Book 1 - Book Review
It's 1453 Italy, and gorgeous 17-year-old novitiate Luca Vero is accused of heresy for using logic. As punishment for his crime, Luca (who is rumored to be a changeling because he's so much cleverer and more beautiful than his thought-to-be barren parents) must join a secret order to investigate possible demonic activity across the papal realm.
Valkyrie Rising, is about 16-year-old Ellie Overholt, who visits her grandmother in Norway for the summer. Young men around the country are disappearing, and the rumor is that mythological Valkyries -- females who capture young men to be dead "soliders" to take to Valhalla, the afterlife, ruled by Odin -- are responsible