DCI Mark Lapslie is one of those grumpy, rumpled detective characters, with a slight twist. He has synaesthesia - sounds instantly trigger taste sensations. Which makes participating in the world profoundly difficult. The condition is so out of control that he's had to move to an isolated cottage, communicating with his colleagues via technology, keeping the noise at bay so that he can at least function a little. His wife has left him, taking their children with her, he's lonely, fraught, struggling to cope with the condition and the restrictions it places on his life.
Carl Whittley is lonely and bitter, struggling to cope with the reality of being sole carer for his invalid father. While he's doing the cooking, cleaning, colostomy bag changing, and all the personal care, his mother has left and is pursuing her career as a forensic psychologist. In some ways it makes a lot of sense that Carl's planning his third murder very early on in the book.
That last observation isn't much of a spoiler as McCrery doesn't write whodunnit style books, rather they are more an exploration of why. Why Carl Whittley would torture a glamorous TV presenter to death, blow up some poor innocent bloke in a railway station, and still be planning more mayhem. Why Mark Lapslie would try to stick with his job of Police DCI in the face of a personal disability that makes his every hour a nightmare. And one of the biggest mysteries? Why Lapslie's Chief Superintendent would think that putting him in charge of two seemingly unconnected events would provide the media pressure straw that would finally break Lapslie's back and remove him from the police force once and for all.
The synaesthesia aspects of the Lapslie series are the obvious hook that makes them different from other British, grumpy, rumpled, cynical and rather world-weary detective stories. The other difference is that idea of the who being known by the reader up front, and the books being less of a journey to the discovery, and more a look at the characters, their motivations, and ultimately, the way in which the detective get's the bloke the reader already knows all about. There's often traces of quite black humour in this series as well, although in this particular book you'll have to dig a little deeper to find it, and you may also need to have a fairly high tolerance for graphic descriptions. To be frank, there's very little about Carl and his activities that can be explained, or even vaguely quantified, and at the same time there's something rather bleak about the dogged way in which Lapslie pursues his perpetrator.
Not that TOOTH AND CLAW itself is bleak, this is really a very readable, absorbing and interesting entrant in a series that is definitely well worth pursing. I suspect it is, however, one of those series that would be best read in order, as the way that Lapslie's synaesthesia affects his life, his ability to do his job, and everyone around him does ebb and flow, and you need to understand how that all works to get an understanding of him overall.
The series in order:
Still Waters (aka Core of Evil)
Tooth and Claw