Death of a Nag by M.C. Beaton

A busman's holiday for Hamish . . .
After losing both his promotion and the lovely Priscilla Halburton-Smythe, Hamish Macbeth decides the best cure for a broken heart is a week's break at the charming coastal village of Skag.
When he arrives at the Friendly House B&B, however, he finds the ambience chilling, the food inedible and his fellow guests less than neighbourly. They include the annoying Miss Gunnery; a family from London; and Bob Harris, who so nags his wife that everyone wants to kill him. And then somebody does.
Now it is up to Hamish to act - to dig deep into the past and deliver something more daunting than merely the culprit: justice.
Praise for M.C. Beaton:
'The books are a delight: clever, intricate, sardonic and amazingly true to the real Highlands' Kerry Greenwood
'It's always a special treat to return to Lochdubh' New York Times