Bowles referred to this quote from Franz Kafka in Christopher Sawyer's 1989 biography, An Invisible Spectator, when describing the process of writing The Sheltering Sky:
I would write it consciously up to a certain point, and after that let it take its own course. You remember there's a little Kafka quote at the beginning of the third section: "From a certain point onward, there is no turning back; that is the point that must be reached." This seemed important to me.
It is indeed in Book Three that one has the sense of Bowles loosening his reins on the story and letting it take its own course. It feels almost as if the author is being led hither and thither across the dunes by Kit as she loses her grip on rationality and submits to whatever her primitive self allows.
It is at the end of Book Two that Bowles reaches the point of "no turning back". For with Port's death, the event with which the novel might have ended, Bowles realised he hadn't finished: 'The death of the main character," he says in An Invisible Spectator, does not make the book satisfactory. The book has to go on.' For Kit, this point had certainly been reached: there was no turning back.