First, read Whisper Man as the Shadows could be read by itself, but will be much better if you have already read the first book involving these characters to understand the back story.
The Shadows starts out with Paul returning to the childhood town where he grew up and then escaped from those memories for 25 years. His mom is dying and that is the absolute only reason he chances returning. The town looks even more dead than it did.
A boy has been killed and left with many, many stab wounds. What makes it unusual is that other murders have occurred in towns not too far away that are very similar. Who is behind these ritualistic killings and is it the same person or being that was involved in the murder that occurred when Paul was young?
It certainly keeps your interest to the very end. Good author to follow!