Illea is a kingdom divided by castes such as being an artist, a farmer, or a factory worker, ranked from 1-8, with 8 being the lowest caste.
America Singer is a Five and a member of the Artist caste. America’s mother pressures her about undergoing the Selection, a process where the Prince will choose his Queen. America does not wish to participate, as she is in love with Aspen, who is a Six, a member of the lower caste. Aspen breaks up with America when he realizes she is not good enough for her. This pushes America to join the Selection where she will compete with 34 other girls for the Prince’s affections.
America quickly makes friends with Marlee and others but her ability to draw attention from members of the palace causes Celeste to quickly despise her. America does not wish to marry prince Maxon but she accidentally comes across him in the Palace gardens.
America realizes the extent of her feelings when she soon becomes jealous when Maxon spends times with the other girls as well.
America comes across Aspen again one day and he informs her that he has moved up the ranks to become a member of the guard. America’s feelings for Aspen come rushing back and she is confused who has her heart – Maxon or Aspen? However, she knows that if she pursues a relationship with Aspen whilst being a member of the Selection, which is equivalent to treason.
At the same time, rebels are attacking the Palace, which pressures Maxon to narrow down the Selection to six girls, known the Elites. America makes hit though as an Elite and realizes that she wants to be with Maxon. As such, she tells Aspen that she does not want to be with him. However, the book ends with Aspen declaring to fight for America.