This is America Singer, she lives outside the kingdom of Illea in a world with a caste system. There are eight castes America and her family are Fives. (Ones are the highest Eights are the lowest) She has a boyfriend Aspen who is a six. Aspen and Americas family urge her to enter in something called The Selection.
The Selection is a competition, 35 "random" girls are chosen to go to the palace of Illea and compete. For what you may ask, Prince Maxon Schreave. The girls stay/live at the palace and the Prince "dates" each one to decide who he marrie. When the competition comes down to six those six are called The Elite and if you get in your caste becomes an automatic 3 unless before this you were a Two. America enters to please everyone but is extremely shocked and scared when she gets into this competition.
Before she leaves America gathers the few items she needs. Her and Aspen break up for different circumstances. America will be getting money sent back to her family and will live a luxurious life but in all the same America is sad to leave her family.
America arrives at the palace after her journey and is shocked to see as many people are waiting just to catch a glimpse of these girls. The girls are shown their rooms and all given makeovers to be presented to the Prince the following day. On accident that night America meets Maxon. She feels very stressed and begins to have a panic attack but the guards won't let her outside so Maxon discovers the situation and forces them to let her outside. She calls him names which surprisingly intrigue him.
The next day when Maxon formally meets all the girls when talking to America the come upon an agreement. He will keep her at the palace as long as possible so she can get the money sent back to her family and in return she will help him find a wife and tell him who to stay clear of. He agrees and on that day sends home about eighteen girls who he does not feel a "spark" with.
As time goes on and more and more girls are sent home Maxon and Americas friendship grows they meet and talk quite frequently and even have a signal. When they need to talk they pull on their ears since there are people around quite frequently. He will secretly visit her room at night. But when Maxon develops feelings for America it becomes an entirely different game. One where she has to decide what to do with her feelings.