The Uglies (The Uglies Trilogy - Book 1)
by Scott Westerfield

Tally Youngblood lives in a futuristic society that acculturates its citizens to believe that they are ugly until age 16 when they’ll undergo an operation that will change them into pleasure-seeking “pretties.” Anticipating this happy transformation, Tally meets Shay, another female ugly, who shares her enjoyment of hover-boarding and risky pranks. But Shay also disdains the false values and programmed conformity of the society and urges Tally to defect with her to the Smoke, a distant settlement of simple-living conscientious objectors. Tally declines, yet when Shay is found missing by the authorities, Tally is coerced by the cruel Dr. Cable to find her and her compatriots --or remain forever “ugly.”