The Rebel Prince (The Season Series #3)

Forced to sail to the sun-drenched kingdom of Ardalone to fulfill a marriage alliance, Prince Thomas of Pretania must choose one of the Ardalonian princesses to be his wife. But every choice comes with consequences.
Spurned by Thomas' older brother, Princess Dulciana stands to inherit the throne as she is eldest, but only if she marries an Ardalonian noble. Second-in-line Prince Frederico will do anything to ensure that doesn't happen.
But beyond the palace gates, a rebellion is stirring...and if there's one thing Prince Thomas excels at, it's stirring up trouble.

WARNING: MAJOR SPOILERS FOR THE SEASON SERIES! (Though I'm going to do my best to ensure you can read as a standalone if you don't want to read the first two.)