IF BAIN IS Truman's ghost, he won't admit it, but he provides enough clues to support a strong circumstantial case. He states his involvement with the series "for a well-known person" began in 1980 and continues, "I've been writing novels in this series ever since, a book a year, most of them well reviewed and appearing on many bestseller lists throughout the country." How many other candidates for a frequently bestselling book-a-year mystery series beginning around 1980 are there?