Of Curses and Hearts by E.J. Kitchens

Princess Blythe’s heart is made of glass, and someone’s out to break it—literally.
Prince Murdock’s heart is the prize of the princess tests, and someone’s out to steal it—fatally.
Prince Murdock—Dox—must marry by his twenty-fifth birthday a month away, but with no bride in sight and fake princesses in abundance, his eccentric fairy godparents arrange a series of princess tests to help him find true love with a true princess. Though worried about what tests his godparents will concoct, Dox is much more comfortable scoring a test than risking falling for a pretty face with a black heart. His kingdom depends on his good sense, after all.
Cursed with a heart of glass and a prophecy of doom, Princess Blythe has spent her life terrified of bumps, falls, sudden temperature changes, and falling in love. When a mad scientist intent on studying her one-of-a-kind heart forces her to flee the medical academy where she’s a student, she’s determined to do whatever is necessary to return home. But the coachman who helps her escape isn’t who he seems, and the fae-enchantress who cursed her is looking to break more than a heart—she’s planning to break kingdoms.
Blythe must decide whether to cling to her fears and her cushions and continue home or risk falls, life, and love to save kingdoms—and maybe win a prince’s hand in marriage. Will the prince break her heart, or will she win his?