Hospitality and kindness
Princess Eadlyn is seen as a very strict princess, without feelings for others than herself. The country doesn't love her because of this, and this fact becomes clear to Eadlyn after the parade, when the crowd throws food at her, insults her, and demands jobs. The case worsens when Eadlyn chooses to eliminate 11 of the selected men, as she is then seen as even more cold hearted than before.
Eadlyn's lack of kindness and compassion is a constant obstacle in the story, and Eadlyn can't manage to open up to the selected men about her feelings. When Eadlyn later meets Camilla, Ahren's girlfriend, she breaks. She hates how compassionate, kind and sweet her fellow princess is, as those are all characteristics Eadlyn wishes she had. Eadlyn must constantly battle the consequences she faces because of her behavior, and it is therefore one of the themes Kiera Cass is trying to broadcast through the book: be kind, always.
Accepting and finding youself
Eadlyn spends a lot of her time looking at her friends, family and peers. She constantly compares herself to others and is even described as a person who "wields her powers as a sword" instead of "handling her powers with humility," like Camilla does. Eadlyn strongly dislikes Camilla because of how good of a person she is, and envies that the people love her.
In the end, she understands that she has to embrace who she is, and love herself, without trying to become another person. She understands that she should work to become a better person, without mimicking others to get accepted.
Love
The theme behind the whole book is, of course, love. Everyone around Eadlyn seems to have it. Maxon and America, Eadlyn's parents, are constantly showing each other love, which constantly reminds Eadlyn what she doesn't have. To make matters worse, Eadlyn's brother also goes off and marries Camilla, because he believes he has found true love as well.
The fact that Eadlyn is the only person left without a partner has made a space in her heart open and vulnerable, asking if it might be something wrong with her. Might she be an unlovable person, simply unworthy of love? Even though Eadlyn's love story doesn't end in this book, quite a few things are clear: Eadlyn is perfect just the way she is, and someone will come along and put the ring on her finger.
