Atlantia

by Ally Condie
Lexile:  680
Genre:  Science Fiction/Fantasy

Rio and Bay have grown up together in the world Below.  Now the time has come when they must make a choice:  do they go explore the unknown world Above or remain Below forever?  Rio has always known that when the time came, she would want to go Above, but now their mother has died and Bay has made her sister promise that they will remain Below together.  When the moment of decision comes, Rio announces her intention to stay Below, but Bay unexpectedly chooses a life Above.  Rio is left trying to figure out why her sister made the choice she did and how to make a life for herself alone.