The Uglies Trilogy is about a future dystopia where everyone gets the Pretty Operation at age sixteen. The books are centered around Tally Youngblood, a teenage girl who at first wants nothing more than to become Pretty, but discovers that the Operation is hiding a dark secret.
The Uglies series is set at least three hundred years in the future after our current civilization, known as the Rusty era, was destroyed. The survivors of the "Rusty Crash" established cities much smaller and spread much further apart than the Rusty cities of the past, each of which is independently governed with limited travel between them.
At the age of sixteen, each "Ugly" undergoes a surgical Operation to make them "Pretty" that gives them benefits such as a stronger immune system and boosted reflexes as well as beautiful, well-proportioned, symmetrical bodies based on international standards decided on by the global Pretty Committee. Unknown to the general populace, they are also given lesions, tiny scars in the brain that "turn off" creative thinking and violent tendencies, making most Pretties peaceful, compliant, and brain-damaged.
Some Pretties, however, have the lesions removed. These Pretties enter jobs that require quick-thinking, such as firefighters, surgeons, and Special Circumstances.
Special Circumstances are organizations that protect cities from messy, unpredictable external threats that Pretties aren't capable of handling. The agents of Special Circumstances, called Specials, are given surgeries that make them much physically stronger and faster than normal humans as well as a terrifying "cruel beauty" that commands instant respect in all who see them. They are the only ones who know about the brain lesions and do everything in their power to keep it that way.