Fifth Grave Past the Light (Charley Davidson #5) by Darynda Jones

Charley Davidson isn't your everyday, run-of-the-mill grim reaper. She's more of a paranormal private eye/grim reaper extraordinaire.

However, she gets sidetracked when the sexy, sultry son of Satan, Reyes Farrow, moves in next door. To further complicate matters, Reyes is her main suspect in an arson case.

Charley has vowed to stay away from him until she can find out the truth...but then dead women start appearing in her apartment, one after another, each lost, confused, and terrified beyond reason. When it becomes apparent that her own sister, Gemma is the serial killer's next target, Charley has no choice but to ask for Reyes's help.