To Kiss a Demon by Stephanie Rowe

Buckle up for another high-stakes paranormal roller coaster from bestselling author Stephanie Rowe, in which an immortal assassin falls for the adorably sassy wraith he’s supposed to kill.

When Paige quit her job as Satan’s minion, she thought she was finally free. But when she accidentally incinerates an angel, she discovers she’s on the fast-track to becoming a soulless, evil wraith. The only way to save herself? Enlist the help of the deliciously sexy shadow warrior sent to push her over the edge.
To save his brother, Jed Buchanan sold his soul to Satan Jr. for all eternity. But when the immortal assassin winds up in Paige’s bedroom during a botched mission, the sassy temptress offers a possible way out if he’ll team up with her.
Everyone from heaven to hell wants to get their hands on the weapon Paige is becoming, and time is running out. Can the tormented assassin find the peace and love he’s always desired with an irreverent wraith who refuses to give in to her dark side?