Blood Sympathy (Joe Sixsmith, Book 1) by Reginald Hill
PI can mean many things, but can it really mean a balding, middle-aged lathe operator from a high rise in Luton? Joe Sixsmith thinks it can.
His Aunt Mirabelle thinks you'd have to be crazy to hire him, and Joe's current clients certainly fit the bill. One's confessing to the brutal murder of his whole family; another thinks she's a witch. Next to them, the two heavies who believe Joe is hiding their illicit drugs seem almost normal.
As Joe stumbles his way through bodies, gangsters and hostile police officers, he is protected by a combination of sheer luck and the help of a new lady friend. And soon it seems like he might just surpass everyone's expectations...