Mystery: Death of a Cozy Writer by G.M. Malliet

From his eighteenth century English manor, rich Sir Adrian Beauclerk-Fisk writes mysteries and disinherits his four spoiled children in turn. At an engagement dinner, he announces his secret marriage to beautiful Violet, once charged with her husband's murder. Within hours, eldest son and appointed heir Ruthven is found cleaved to death by a medieval mace. Since Ruthven is generally hated, no one seems too surprised or upset―least of all his cold-blooded wife Lillian.
When Detective Chief Inspector St. Just arrives, a deadly calm goes beyond the usual English reserve. Soon Sir Adrian is found slumped over his writing desk – an ornate knife thrust into his heart. Using Cornish brusqueness and brawn, can St. Just find the killer before another victim falls?
First book of the St. Just Mysteries series.