Uglies (Uglies Trilogy, Book 1)

Everybody gets to be supermodel gorgeous. What could be wrong with that?
Tally is about to turn sixteen, and she can't wait. Not for her license -- for turning pretty. In Tally's world, your sixteenth birthday brings an operation that turns you from a repellent ugly into a stunningly attractive pretty and catapults you into a high-tech paradise where your only job is to have a really great time. In just a few weeks Tally will be there.
But Tally's new friend Shay isn't sure she wants to be pretty. She'd rather risk life on the outside. When Shay runs away, Tally learns about a whole new side of the pretty world -- and it isn't very pretty. The authorities offer Tally the worst choice she can imagine: find her friend and turn her in, or never turn pretty at all. The choice Tally makes changes her world forever.