The Stolen Kingdom by Jillian Boehme 

For a hundred years, the once-prosperous kingdom of Perin Faye has suffered under the rule of the greedy and power-hungry Thungrave kings. Maralyth Graylaern, a vintner’s daughter, has no idea her hidden magical power is proof of a secret bloodline and claim to the throne. Alac Thungrave, the king’s second son, has always been uncomfortable with his position as the spare heir—and the dark, stolen magic that comes with ruling. Maralyth becomes embroiled in a plot to murder the royal family and seize the throne, a cat-and-mouse chase ensues.