C.S. Lewis influence is so broad and some big that it takes some space to cover some of it. This post below really is just comments about some of his work. The specific question, "Is C.S. Lewis a Literary Influence" is covered in a post dated July 13th, 2018. Click here to see that post.
Click covers of Screwtape Letters and Mere Christianity to see reviews
C.S. Lewis's breadth of impact and influence on the literature of our time is significant. His Oxford education, personal character and creativity is only a starting place.
He knowledge of important literature is deep, and his skills as a theologian, poet, fantasy and science fiction writer. He has brought the genre he works in together to bring his message and a good example is how his writings in fantasy stimulates creativity but also gives new meaning to core values.
His understanding of what he writes is deep and he draws from personal experience in his own religious and personal experiences. This connects him to those who also have struggled. .
C.S. Lewis many quotes teach deep lessons. An example is when he said "the good of literature is that we want to to be more than ourselves. We want to see with other eyes to imagine with other imagination, to feel with other hearts, as well as with our own".
Chronicles of Narnia and his ample body of fantasy writings are examples of how we really do "imagine with other imagination".
In his writings on Christianity we really do learn to "feel with other hearts as well as our own".
"Screwtape letters" is just one example of how his works help us to "see ourselves with others eyes". It is a masterpiece of satire that enables you to consider how you would look to the senior tempter of the devil represented by Screwtape,
Clive Staples Lewis (1898–1963) "was one of the intellectual giants of the twentieth century and arguably one of the most influential writers of his day. He was a Fellow and Tutor in English Literature at Oxford University until 1954, when he was unanimously elected to the Chair of Medieval and Renaissance Literature at Cambridge University, a position he held until his retirement."
C.S. Lewis is an author that has had a impact over several genres of literature.