Pretties (Uglies #2) by Scott Westerfeld

After Tally turns Pretty, she enjoys the Pretty lifestyle in New Pretty Town: parties all the time, getting drunk, doing mindless Pretty things. But a visitor from her past comes to her during one of the parties and tells her that something is hidden in a room. She goes on a hunt with Zane, one of her new Pretty friends, and discover two white pills and a note she had written to herself before she decided to turn Pretty. Zane and Tally split the pills, each taking one, and soon their minds are changed and everything is more bubbly. Other people in their clique (known as the Crims), notice the change and want to know how else they can be bubbly and soon everything becomes a competition for who can become more bubbly. Eventually, the Crims do the most bubbly thing ever: they break through a hovering ice rink, which sends a signal to the Smokies that the pills did work. However, Zane has come down with terrible headaches and Special Circumstances are breathing down Tally and Zane's necks, leading them to be trapped in bracelets they can't escape, no matter how much weight they lose. With Zane's increasing headaches, will they be able to escape back to the New Smoke for a cure for Zane or will they end up trapped in New Pretty Town forever?