But I'm not sure this automatically debunks anything that later interviews are contradictory on. From my understanding the book is the result of contemporary interviews done for a magazine that never happened that would have been effectively a promotional piece for the film.
I don't think that's correct.
Cinefantastique's analyses, as I recall them, tended to be rather more critical and in-depth than just promotional fluff.
Starlog, its main competitor, tended to be positive and enthusiastic in its coverage of new stuff, but I had the impression that CFQ's coverage had more of a hard-hitting edge.