The King of Attolia By Megan Whalen Turner - The Queen's Thief #3

Through scheming and outright theft, the Thief of Eddis has become the King of Attolia. Eugenides wanted the queen, not the crown, but he finds himself trapped in a web of his own making.

Despised by his court, and apparently his bride, Eugenides ensnares a naive young guard in the web of intrigue that surrounds him. Struggling to find his footing, the guard, Costis, knows he's a pawn. What he doesn't know is how the king means to play the game.