“The Spectacular” (Dutton, out now). The novel follows Marian, a plucky young dancer in the 1950s, who defies her family’s expectations when she runs away from home to join the Rockettes — right as a mysterious bomber is terrorizing the city, leaving explosives in some of the Big Apple’s most iconic landmarks.Davis interviewed about a dozen Rockettes in the course of her research, but Lachenauer proved to be an invaluable resource, plying her with old programs and photos from her time there, as well as reading a manuscript and providing notes for Davis to make her tale as authentic as possible.“I was really intimidated because I don’t have a dance background,” Davis explains.