The One (The Selection #3)

When she was chosen to compete in the Selection, America never dreamed she would find herself anywhere close to the crown—or to Prince Maxon's heart. But as the end of the competition approaches, and the threats outside the palace walls grow more vicious, America realizes just how much she stands to lose—and how hard she'll have to fight for the future she wants.

The One is book number three in The Selection series by Kiera Cass.