Greene, in fact, thought The Quiet American was superior to The End of the Affair. He said so in his autobiographical Ways of Escape.
The End of the Affair was a greater success with readers than with critics. I felt such doubt of it that I sent the typescript to my friend Edward Sackville-West and asked his advice. Should I put the book in a drawer and forget it? He answered me frankly that he didn’t care for the novel but nonetheless I should publish — we ought to have the vitality of the Victorians who never hesitated to publish the bad as well as the good. So publish I did. I was much comforted by words of praise from William Faulkner, and I was later grateful for the two years’ practice I had had in the use of the first person or I might have been afraid to use it in The Quiet American, a novel which imperatively demanded it, and which is, technically at least, perhaps a more successful book.
Greene briefly discussed his art and his Catholic faith in an interview with The Paris Review in 1953.
Memorably, he said:
No, one never knows enough about characters in real life to put them into novels. One gets started and then, suddenly, one cannot remember what toothpaste they use; what are their views on interior decoration, and one is stuck utterly. No, major characters emerge; minor ones may be photographed.
“Do you work at regular hours?” he was asked.
“I used to; now I set myself a number of words,” he said.
“Five hundred, stepped up to seven fifty as the book gets on,” he said. “I reread the same day, again the next morning and again and again until the passage has got too far behind to matter to the bit that I am writing.”