In this sequel to Cycler, readers are reintroduced to Jill and Jack. Having just finished high school with a major trauma at the prom, Jill is finally getting a better handle on the fact that she shares her body with Jack. Once a month, for four days, her body morphs into a male and his personality comes to the fore. Up until now, her parents arranged for him to be locked in her room so no one would know about the situation.

Jack slowly learned how to get out into the real world. While she can't see what happens during "Jacktime," he has full access to all of the memories that accrue when she is in charge of their shared body. This is one of the reason why he has fallen in love with her best friend Ramie.

Ramie is off to New York to start her first year at FIT, and Jill is going to come along and be her roommate. Instead of going to school, she wants to get a job and spend time sorting out the complexities of her life.

Besides sharing her body with an uber-sexed guy, Jill is also missing her boyfriend Tommy who is taking an opportunity to drive across the country. He had hoped Jill would have joined him, but he understands when she opts for the safety of living with Ramie and Jack in Brooklyn.

What is interesting about this sequel is that Jack and Jill have started to really move beyond their distrust and dislike of each other. They are really starting to think less about the other being an enemy fighting for control of their body and the ability to live their lives as they choose. They start to settle into a more common view of the world and almost start looking at each other like twin siblings. At times, this means stepping up to help the other even when it means sacrificing your own views.

Jack really sees a lot of growth when he meets a group of guys with a chart highlighting the underdog girls each has had sex with. The goal is for them all to get as many girls as possible and have a lot of cross-over. Jack is surprisingly horrified this and finds that he is much more of a feminist than anyone would have thought.

He also must deal with the challenge of overcoming jealousy as Ramie's fashion career starts to take off, pulling her off to fashion shoots in Europe.

Jill on the other hand is really starting to come out of her shell. She has always played things safe when it comes to relationships, and she is starting to consider more opportunities to experiment with guys. Unfortunately, that doesn't always mean making the right choices.

She is also surprised by the changes that are coming about for Jack, who has a partial detente forming with their parents.

This is really a coming-of-age story. Of course, it is made more unique by the situation for Jack and Jill, but in the same vein, it also highlights how people can grow and adapt. I think that Jill and Jack are both very strongly developed and are actually pretty regular teens outside of the fact that they share a single body. Each is struggling with really understanding who he or she is and wants to be. Through the challenges they face in the book (both separately and together), they become more comfortable with themselves and are ready to go forward with their lives.