Irwin Fletcher It's a film novelization, which means that they were making a movie from an original script and as part of the merchandising campaign they hired an author to adapt it into a tie-in paperback. It was a very common practice, especially in the 70s, 80s and 90s but seen less these days except franchises like Star Wars and Star Trek which have kept up the practice into recent years. There are some great ones but as a rule they were just sort of rushed jobs by hired gun writers who sometimes only had a script or partial cut to work with and were mainly put out as merchandise rather than literature. The hope was you'd love the movie so much that you'd want to buy the book to relive it while you wait forever for it to come out on VHS. They are much more interesting these days for their novelty and the fact that they, either through author invention or the inclusion of scenes that wound up on the cutting room floor, expand on classic films. Not always for the better.