I think this one is my favourite of the series so far. It leads on pretty much from book 2, with a character in a coma (I’m trying not to give spoilers for book 2). When the character wakes, they have regressed to a childlike state and McLean feels obliged to look after them. Meanwhile there is a spate of suicides across the city, all deaths by hanging and something is not right with them. McLean is having his usual luck with his career (ie none) and he has been transferred to the vice unit, where he investigates the death of a pimp.
On a gruesomeness scale, book 3 is not as gross as book 1 but it has some very gross moments. I also feel like I now know way too much about hanging. The supernatural element is still there and it really helps make the book stand out, as well as giving the series a subtle arc of sorts.