Jill McTeague suffers from a unique condition, in which she transforms into a teenage boy for four days of every month. As Jill, she enjoys a fairly ordinary life, yearning for a prom date and freedom from her bizarre circumstance. As Jack, he stays locked in the bedroom for the duration, a dirty little secret known only to Jill’s parents. But Jack’s growing rebellious and stronger with every transformation. Can Jack and Jill find some sort of balance, even as they both struggle with teen hormones and conflicting desires? An intriguing book, Cycler sets up a fascinating premise and populates it with memorable characters. Unfortunately, it ends just as things are truly getting interesting, leaving room for a sequel. Regardless, it’s a thought-provoking exploration about identity, sexuality, and gender differences.