At the beginning of the story, Tally Youngblood is only a few months away from her 16th birthday, so she is still an Ugly, but she longs for her birthday to arrive because she misses the only friend she's had since she became an ugly - her best friend, Peris. Always playing tricks and sneaking around when she shouldn't, Tally decides to visit Peris in New Pretty Town, but when she arrives, she realizes that Peris is not the same. But although she lost this friend, she meets a new friend, Shay, on on her way back to Uglyville. After their meeting, the two are inseparable until Shay tells Tally that she doesn't want to be pretty; instead, she's leaving the city to join a rogue group (the Smokies), avoiding the permanent beauty alteration altogether. She wants Tally to come with her. Of course, Tally refuses to go because her only dream has been to become a Pretty, leaving Uglyville behind and joining Peris. Her dreams are dashed, though, because on the day she is supposed to have her surgery, she is blackmailed into finding Shay and the Smokies. She must betray them and turn them into the authorities because if she doesn't, she will remain Ugly forever.
Once in the Smokies camp, however, she meets David, a boy who's grown up outside of the city limits. He shows her that beauty doesn't necessarily come from the outside, and although he doesn't know it, he changes her mind about the betrayal. But, even though she decided against it, the authorities still come and capture the Smokies, causing Tally to think of a plan that not only saves her friends, but also absolves her guilt.
What I liked about the novel was that there were a lot of connections I could make to the modern society, especially the focus on outward appearance and its impact on life. For example, in 2016 there was a scientific study done to find the most beautiful face, where the scientist used the Greek-based number Phi, which represents aesthetically pleasing proportions. I also liked the symbolism interwoven throughout the story, specifically the wild orchids and the boulders.