They Never Came Home

Duncan is best known for her novels of suspense for teenagers. Some of her works have been adapted for the screen, the most famous example being the 1997 film I Know What You Did Last Summer, adapted from her novel of the same title. She has stated her distaste in interviews at her young adult novel becoming a horror comedy film.

In 1989 the youngest of Duncan's children, Kaitlyn Arquette, was murdered in Albuquerque, New Mexico, under suspicious circumstances. Who Killed My Daughter? relates the facts and conjecture about the still unsolved case.Duncan has said her "dream is to write a sequel to who killed My Daughter? to give our family's true life horror story a closure. Of course, for that to be possible, Kait's case must be solved."

The 1971 children's book Hotel for Dogs has been made into a movie, released in 2009, starring Emma Roberts. Duncan herself appears as an extra in the crowd scene.