An Exchange of Hearts

All Princess Celia has ever wanted is to be left alone. She's built her own enchanted tower out of glass and thorns, where she can keep the world outside while exploring her magical gifts, far away from royal expectations and an arranged marriage. But she's woven her protections too well -- and even though she's finding her tower lonely after so long, she can't undo her spell alone. Stefan only agreed to accompany his brother in order to provide magical help.
After all, rescuing the princess of the glass castle is supposed to be Crown Prince Garald's quest, not his magician's. But the quest has already claimed lives, and Stef can't let his brother face the peril alone. Besides, he likes a challenge. Unlocking the spell will require Stef and Celia to use all their power and find the key in an exchange of hearts.