King of the Underworld (King of the Underworld, #1)
R.J. Kane
Sephie, named for the Queen of the Underworld, Persephone, she's quickly finding out how she's destined to fulfill her namesake's role. Adrik is the King of the Underworld, the boss of all bosses in the city he runs.
She was a seemingly normal girl, with a normal job until it all changed one night when he walked through the front door and her life changed abruptly. Now, she finds herself on the wrong side of powerful men, but under the protection of the most powerful among them.