The Rattle-Rat by Janwillem van de Wetering

Douwe Scherjoen was a well-to-do livestock dealer from the remote Dutch province of Friesland. Then his corpse was found, half-charred by flames, floating in a dory in Amsterdam's harbor. No one knows why he was in the nation's capital, far from the bucolic pleasures of his native village of Dingjum. But since Grijpstra is Friesian by birth and can understand the dialect, he and his partner de Gier are dispatched to find the killer—or at least the motive for the crime. And they discover that while no one, not even his wife, liked the victim, the culprit is the unlikeliest suspect of all.