Scott Westerfeld has done it again. In a very short space he has created a world in which I would like to go visit again. We meet Kieran & Maria two kids in a "scarcity" class. A class studying the past in which humans had to deal with things such as sleep, illnesses, disease, etc. Kieran chooses to study sleep and Maria chooses hormonal imbalance. What they learn about themselves and their world are life changing.