An interesting book. Ties up a few of the plot hooks from earlier books. In this one John is asked to look into the history of the Nightside. No-one really wants him to do this and a few of the people opposed to this are willing to kill him to stop him.
To help him with his investigation he gets the Madman (who has seen too much and now his madness can alter the world around him) and Sinner (who traded his soul for love and even though the woman he loves is a demon he still loves her so he is excluded from heaven and hell). This book introduces you to more characters, some more of the secrets and lies involved and tells us more about what John's background and possible future is.
I really do enjoy this series and want to read more of them.