Happy Release Day to Forevermore by Kristen Callahan
Isolate and alone, Sin Evernight is one of the most powerful supernatural creatures in heaven and on earth. As an angel of vengeance, he hunts down the darkest evil, but when his long-lost friend, Layla Starling, needs him, he vows to become her protector. Even though she will be horrified by the man he has become.
Now a famous singer and the toast of London, Layla believes that Sin is only here to guard her from rabid fans and ardent suitors. However, the truth is far more sinister. Desperate to avoid losing Layla a second time, Sin will face a test of all his powers to defeat an unstoppable foe—and win an eternity with the woman he loves.