Winter by Marissa Meyer

Princess Winter is admired by the Lunar people for her grace and kindness, and despite the scars that mar her face, her beauty is said to be even more breathtaking than that of her stepmother, Queen Levana.

Winter despises her stepmother, and knows Levana won’t approve of her feelings for her childhood friend―the handsome palace guard, Jacin. But Winter’s been undermining her stepmother’s wishes for years. Together with the cyborg mechanic, Cinder, and her allies, Winter might even have the power to launch a revolution and win a war that’s been raging for far too long.