Finished this yesterday. It's unusual for me to keep thinking about a book after I've finished it. I read so many that I normally just grab the next one in my pile. But this one, oh my God it's so unbearably tense. I have read the whole Jack Caffrey series and fortunately this one is not as gruesome as the previous ones. I thought it was very tightly plotted, loads of twists and also moved the whole disappearance of his brother story arc on.
In summary it's bloody good but don't read it if you scare easily.