The Uglies trilogy by Scott Westerfield technically has a fourth, Extras, but it does not revolve around the main character Tally as the others do. The first three books follow Tally in a futuristic society where all children are forced to live in the outer rim of society until they turn 16, at which time they undergo surgical operations to become "pretty." Turning pretty means being able to join the party society in the city.
At first Tally is ready to join her older friends, but she ends up running away and finding a group that is determined to keep the looks they were born with. The rest of the series has Tally struggling to discover who she can trust, deciding who she wants to be, and finding out where she belongs.
I thought this was a really interesting book series. A lot of the things in the books were lessons and comparisons to what people today think is important, but the books didn't feel overly moralistic. There was enough action and suspense to keep me interested and wanting to read the next book, and it was fun reading about the kind of party games going on.
I recommend these books to anyone interested in this combination of action and inner vs. outer beauty, but it will probably interest underclassmen in high school the most.