Urâții by Scott Westerfeld

In a future where all sixteen-year-olds undergo surgery to become flawless “Pretties,” Tally Youngblood longs for the change until her friend Shay flees to a rebel settlement called the Smoke. Coerced by a secretive authority to betray the rebels in exchange for her own operation, she infiltrates the Smoke and learns the surgery implants brain lesions that suppress independent thought. Forced to choose between conformity and freedom, she sparks a chain of events that challenges the society’s control.