Neil D, I know we shouldn't go off-topic too much, but as an ex-librarian I am interested in finding the Scottish detective story author and helping you to correctly attribute the quote.

Male or female detective? Have any of the books been made into movies or TV shows? Is the author in this list? Scottish crime fiction writers

Any more clues you can give us?

You can PM me with more clues if you want so that we don't sully this topic with an unnecessary detour.