The Wrath and the Dawn (original) Renée Ahdieh

In a land ruled by a murderous boy-king, each dawn brings heartache to a new family. Khalid, the eighteen-year-old Caliph of Khorasan, is a monster. Each night he takes a new bride only to have a silk cord wrapped around her throat come morning. When sixteen-year-old Shahrzad's dearest friend falls victim to Khalid, Shahrzad vows vengeance and volunteers to be his next bride. Shahrzad is determined not only to stay alive, but to end the caliph's reign of terror once and for all.