Alfrick Howard Hawks wanted to make this book into a movie. He asked Leigh Brackett to write the screen play which she did. However, his recent pictures had bombed and he decided this was to depressing to be made into a movie. He told Brackett to rewrite the screenplay making it similar to Rio Bravo a previously successful John Wayne vehicle. Brackett under pressure rewrote it. It was completely different from the book.
Richard Draude I have the movie. The opening credit do say it’s based on this book. Based is an ambiguous term in Hollywood. Howard Hawkes and John Wayne made the same movie 3 times. El Dorado is by far the best. Rio Bravo, while based on another short story, is pretty much the same plot. The worst is Rio Lobo. Outside of Wayne, the rest of the cast seemed to be reading their lines off Q cards. These remakes prove Hollywood will keep remaking a movie until they get it wrong. Jackson "BASED" his telling of "The Lord Of The Rings" On JRR Tolkins work. While I live the movies, there are elements Peter ignored, changed, moved around, or made up. The elves coming to Helms Deep is one of those. He certainly, put his spin on the end of the ring. That why so many times people will say I like the book better. Harry brown's story is one of those.
Jim Not uncommon for films to be credited as "based on" another work like a novel but hardly resemble the works they purport to be based on. Most likely the project started life as an adaptation of Brown's novel but the script was rewritten (most likely several times) to please producers, the director or actors or someone else with clout during the production.