C.S. Lewis, Mere Christianity

Suppose I am writing a novel. I write "Mary laid down her work; next moment came a knock at the door!" For Mary who has to live in the imaginary time of my story there is no interval between putting down the work and hearing the knock. But I, who am Mary's maker, do not live in that imaginary time at all. Between writing the first half of that sentence and the second, I might sit down for three hours and think steadily about Mary. I could think about Mary as if she were the only character in the book and for as long as I pleased, and the hours I spent in doing so would not appear in Mary's time (the time inside the story) at all.

[Book IV, Chapter 3, "Time and Beyond Time"]