The Cape Cod Mystery

The Cape Cod Mystery, first published in 1931, is a detective story by Phoebe Atwood Taylor, the first to feature her series detective Asey Mayo, the "Codfish Sherlock". This novel is a mystery of the type known as a whodunnit.

"Phoebe Atwood Taylor can get more fun into a detective story than any writer at present producing, and with all the fun there is a mystery that is baffling for its own sake." -The New York Times

Plot Summary
Dale Sanborn has made a lot of enemies in his career as a muckraking author, philanderer and occasional blackmailer. When he vacations at a cabin in Cape Cod, any of his many visitors—an old girl friend, his fiancée, an outraged husband, a long-lost brother and a few more—the night he died could have killed him, and all of them wanted to. When a respectable Boston matron is involved in the crime, local character Asey Mayo takes a hand and brings the case to a successful, if unexpected, conclusion.

 TL;DR: 

"When a famous author turns up dead, it's up to Asey Mayo to find the killer."                 -storytel.com