Here she explains why she won't dreamcast her new novel, By Blood:
Gabriel García Márquez refused offers for a film based on One Hundred Years of Solitude. He said that a reader, after seeing the movie, would never again be able to see Colonel Aureliano Buendía as anyone but the actor. I have never forgotten that, because it agreed so completely with my experience.Read more about By Blood at the Farrar, Straus and Giroux website.
In a novel, there's a private, interior sense of a story and its characters. Once a film is made, everything becomes physical, actual. Call me weird, but if I deeply love a book, and a movie is made of it, I try never to see it.
It's the same for me when I'm writing: I never think of an actor for a role.
I was explicitly remembering García Márquez in the parts of By Blood where the narrator, an eavesdropper, is trying not to see the actual people he is overhearing, so he can preserve his inner image of them. From pages 23-24:
Over the weeks, a certain picture of the doctor had grown in my mind -- nearing sixty, a slight limp (which I heard as she walked by my door), gray hair, perhaps a bun -- an image simultaneously particular in certain details but vague overall, the way a character in a novel, barely described, can yet occupy a distinct place in one's mind.From another passage, which is on page 69:
... a sudden double-mindedness came over me. Two images of my dear patient began to war in my mind: first the rather ordinary face of the young woman in the elevator (a flushed cheek, a sweaty brow), then the vague yet delicate and lovely place in my imagination in which my dear patient had always lived.
The Page 69 Test: By Blood.