Murder at the Book Fair — Steve Demaree

Two recently-retired detectives, with a love for reading mysteries, find out about a large book fair and head off to check it out. When they return home, each carrying an armload of books, they learn that someone they met at the book fair is dead. The well-past-retirement-age coroner rules it an accidental death, but the sheriff thinks otherwise and calls on the two recently-retired detectives to solve the murder, which takes them to three small towns talking to suspects and people who might have seen something that will help them solve the case. Like the other books in this series, it is a whodunit with twists and turns and a lot of humor.