I'm very much in love with this series, and the third book was probably my favorite. It is fast-paced, the mystery is an interesting one and the secret revealed is very creepy, again, showing how thin is the line between obsession and madness.
And the main character, Billings, is even more likable, sweet, sad, awkward and suffering than before. I'll be so glad if there're more books about him in future. And maybe some happier personal life for him :) Poor guy is always getting caught when he even doesn't do anything. He should do something for a change and not get caught.
I loved the ending; it nearly broke my heart, and then oh, that glimpse of hope. Beautiful.