Murders for Sale by Andre Norton and Grace Allen Hogarth (epub/Kindle/pdf)
When Fredericka Wing arrives in South Sutton, Massachusetts, a tiny New England town, it seems an ideal place for a working summer vacation. She plans on managing Miss Hartwell's bookstore while working on her own writing. She never dreamed she would find a body in a hammock in her own backyard. Someone brutally murdered Catherine Clay, an heir to the Sutton family fortune. And more violence follows. Together with Peter Mohun, a professor at a local college, Fredericka sets out to discover the murderer's identity ... and unravel the secrets of the wealthy and powerful Sutton family!
"Murders for Sale" -- also published under the title "Sneeze on Sunday" -- is one of science fiction writer Andre Norton's rare excursions into the mystery field.