The Kiss of Deception by Mary E. Pearson

The Runaway Princess: Princess Lia is the First Daughter of the Kingdom of Morrighan, a position that traditionally comes with a mystical gift (the "remnant"). Refusing to be a political pawn in an arranged marriage to a prince she has never met, she flees on her wedding day to live a quiet life as a tavern maid in a distant coastal village.

The Two Strangers: Two mysterious, attractive men arrive at the tavern shortly after her. One is the Prince she left at the altar, determined to find the girl who humiliated him. The other is an Assassin sent by a rival kingdom to eliminate her before she can secure an alliance.

The Deception: The unique hook of the book is that both men use aliases. While the reader reads chapters from the perspectives of "The Prince" and "The Assassin," their true identities are kept secret for a large portion of the story, forcing you to try and figure out which man is which as they both grow closer to Lia.