Why Lewis Isn't Focusing on Specific Atonement Theories

Lewis doesn't give a fuller exposition of for example Christology or Soteriology to use two technical terms, the identity of Christ and what Christ has done. And I think it's because he feels it's not actually essential for his purposes. He is trying to give his readers if you like a taster of the deeper understanding of Christ that lies behind Christianity rather than a full exposition of it. But Lewis will always say that the actuality is primary and the explanation of that is secondary.