Nocturnal Animals is far from a straight-forward narrative, as Gyllenhaal plays two roles in the movie: one a scorned author who sees his relationship come to a crushing end, and the second a fictional representation of the author in a book that functions as a metaphor for the aforementioned relationship.
Watching the film and understanding Jake Gyllenhaal’s character, one can kind of comprehend why Tom Ford would want complete creative control of the actor’s understanding of the role.
One could make the argument that this kind of complexity ultimately demands a clear vision, thus the desire for Gyllenhaal to only focus on the screenplay and not the novel.