There were 15 books written, based on Lee Falk's stories, from 1972 to 1975 by Avon Publications.
Those were written by Lee Falk or a ghost writer. Ron Goulart, using the pseudoneum of Frank S. Shawn, later remarked that Falk originally asked Alfred Bester, who had previously worked on the Phantom comic strip when Falk served in the army, to ghost-write a few novels. Bester was not interested, and recommended Goulart for Falk. The covers for the novels were done by George Wilson, previously known for his work on US Phantom comic books. Many of the books were translated into many foreign languages.