I really enjoyed this one, a great start to the cast. I don't remember reading anything else by Sigler to date, but I'll be watching out for the name now.
I like how the ghost wasn't just out for mindless revenge against his attacker, nor just randomly attacking people he comes across (like a revenant). He was very systematic and logical about how he wanted to do his work, which made him feel very unique.
I like the supernatural time limit and I'm glad it didn't end up being really stupid like The Ring (but that's another rant for another day).
And I thought it was cool how he keeps on going, working his way through lesser criminals. Where will he stop? If he could work fast enough, he'd be down to shoplifters and tellers of white lies, and then there would be nobody left.
The one thing that lifted me out of my listener's trance was the claim that he'd killed all of the murderers--is he anchored to just the one city? Why not roam further afield? He's already shown by showing up on the airplane that he's not locally anchored, so why not?