Once Upon a Broken Heart by Stephanie Garber — book slip

Evangeline Fox has always believed in true love and happy endings. When she discovers that her beloved is set to marry her stepsister, she turns to the enigmatic Prince of Hearts for assistance.

In exchange for his help, he demands three kisses, to be given at times and places of his choosing.

As Evangeline fulfills her end of the bargain, she realizes that dealing with an immortal comes with unforeseen consequences, leading her into a perilous journey filled with magic, betrayal, and the quest for her own happily ever after.

First in the 'Once Upon a Broken Heart' series.