Love
One of the major themes in the novel is love, romantic love and family love in particular. The romantic love between Harper and Nick remains yet undeveloped properly but form the beginning it becomes clear that they have feelings for one another and Nick starts to gradually care more and more about Harper and about her wellbeing. Another type of love is between Oliver and Grayson and it is the love between a father and his son. We see that both Nicholas and Oliver are willing to sacrifice everything and everyone to save those they love. This type of loves proves to be destructive as it affects negatively those around them.
Greater good
The characters in the novel, especially Nick, are put to decide if it is worth sacrificing a few lives for the greater good. For Nicholas, the answer is clear as he feel no remorse killing a few if he believes that it will eventually save many more. For Nick however, the question is not easy to answer as he believes that every life is precious. Because of this, he always thinks about the best way to proceed and how to react when he is put under pressure.
