Cage of Tangled Thornes - Thorne Chronicles, #1

An epic, young adult coming-of-age dark fantasy. Magic and unrest has returned to Iosia, and no one in the kingdom is safe... Not the Heir, and certainly not, the Spare. Long ago, Sentinels-shifters blessed by the gods with the ability to transform between human and animal forms-were revered throughout all Iosia. The Onyx magicians, who sought to rule with dark magic and fear, were defeated by the first Thorne King and his loyal Sentinels.
With magic banished, all of Iosia enjoyed peace and prosperity under the rule of the House of Thorne. Now, the Sentinels are shunned, forced to live on the outskirts of society, and in danger of being hunted into extinction because of fear and prejudice. The Undesirables, as the exiled descendants of the once powerful Onyx magicians are called, remain trapped behind the Guardian border wall-forced to live in squalor in the desolate region of Valdisia-a cruel penance for the sins of their ancestors.
Seventeen-year-old Princess Ysabelle, firstborn of King Leopold Thorne and Queen Astrid, is the beautiful and ambitious heir, willing to do anything to attain her birthright-even marrying the enemy-a man who threatens not only her future, but also her heart. While Ysabelle loves being a princess, her younger sister, Dahlia, does not. Sixteen-year-old Princess Dahlia is the feisty, rebellious Spare who longs for a life beyond the castle walls; a life free from the restrictive rules of her royal family and society's judgmental glares-one where she does not have to conceal her disabilities from the world.
A life where she can spread her wings and fly. After centuries of peace, trouble is brewing in Iosia. King Leopold seeks to quell the unrest and prevent war with a royal wedding. For the first time since the Guardian Wall was erected-separating Valdisia from Caelius and the other regions of Iosia-those of Thorne and Onyx blood stand side-by-side in Thorne Castle, but all is not as it seems. Magic exists once more in the Kingdom.
Darkness is lurking; feeding on secrets, seeking to pit sister against sister-Heir against Spare-to alter destinies. Can a Thorne save Iosia once more, or is the real enemy wearing the crown?