Mario Puzo’s “The Godfather” is celebrating its 50th anniversary this year, and writer-director Francis Ford Coppola has marked the occasion by writing the foreword to the novel’s special new edition. Coppola worked closely with Puzo to turn the “The Godfather” into the landmark 1972 movie of the same name. The two remained close collaborators on “The Godfather Part II” and “The Godfather Part III.” Adapting Puzo’s novel with Puzo himself presented some minor challenges for Coppola, who writes in the forward about reservations the author had about scenes that would end up being some of the franchise’s most iconic.

“Not all of my ideas went over so well,” Coppola writes (via Entertainment Weekly). “Mario was dubious about the idea that it was Fredo who betrayed Michael; he didn’t think it was plausible. But he was absolutely against Michael ordering his own brother to be killed. It...