Gregory (The Other Boleyn Girl) makes a hypnotic YA debut with the first book in her planned Order of Darkness series. Set in 15th-century Italy after the Ottoman Empire captured the city of Constantinople, this historical fantasy follows two distinctive 17-year-old protagonists. Luca Vero is an alleged faerie changeling, who is kicked out of his monastery and sent on an ominous mission by the Pope: to document incidents of the uncanny that are believed to be the work of Satan and signs of approaching end times. Isolde is denied her inheritance and trapped in the role of Lady Abbess at a nunnery. Luca's first assignment sends him, his servant, and his clerk to investigate the nunnery, where women have been plagued by visions, sleep disturbances, and stigmata wounds since Isolde's arrival; she and her servant Ishraq are accused of witchcraft. Gregory creates an immersive medieval world that is under the sway of both unfounded superstitions and very real supernatural forces. Though dialogue-heavy scenes are occasionally labored, powerful imagery, picaresque humor, and a polished literary style should captivate mature readers. Ages 14–up. Agent: Anthony Mason. (May)