I could never figure that out either. Especially since you wouldn't need a special effects mega-budget. And at least one of McDonald's books was made into a successful flick, Cape Fear.
My favorite escapist literature genre is the police procedural..especially the 87th precinct novels of Ed McBain. I could never figure out if McGee's alter ego, Meyer, was somehow "related" to Det Meter Meyer...they sound like long separated twins...Well, if I ever want to get a PhD in Eng lit.there's my thesis..
"Cape Fear" was made into two big budget Hollywood hits, one starring Gregory Peck and Robert Mitchum, the other starring Nick Nolte and Robert Deniro, if I recall correctly. Both are pretty terrific, real nail-biters. McDonald's book was not called Cape Fear though, I think it was called The Executioners.