It's not because the books aren't good. They're both very entertaining, and this one (and Sweet Cheat, too, as I recall) contain an element of what's sometimes referred to now as the "woo-woo" factor. In the case of this book, it's a ghost.
Pete Farrell is a two-fisted magazine photographer who's sent to the private island of a rich and successful novelist (is there any other kind?) to take photos for a story to be written by the lovely Laura Ames. The novelist's secretary has recently died a mysterious death, and his new secretary, the voluptuous Cuba, complicates things for Farrell quite a bit. Besides the ghost, the secretary, and the novelist, the island is home to the writer's alcoholic aunt, a housekeeper, and a handyman. There are a lot of sexual hijinks of the 1950s Playboy variety, including a couple of pretty funny sex scenes. Duncan's touch is light, and his style is smooth. If you can get past the '50s attitudes (I can), then this one's fun to read. And it's short, too, the usual 144-page Gold Medal product. I enjoyed visiting it again.