Source-hunters on C.S. Lewis must deal with what James Como called his “alchemical imagination”—his tendency to act like medieval writers who “were in the business not of inventing new material but of transforming existing material.” Schmidt tabulates parallels in Lewis’s writing to two particular sources: David Lindsay’s A Voyage to Arcturus, which Lewis acknowledged as a major influence, and V.A. Thisted’s Letters From Hell, which he claimed to his friend Arthur Greeves he couldn’t get through and gave away after trying to read only once.
"Literary Dependence in the Fiction of C.S. Lewis: Two Case Studies,"
Mythlore: A Journal of J.R.R. Tolkien, C.S. Lewis, Charles Williams, and Mythopoeic Literature: Vol. 35
, Article 7.
Available at: http://dc.swosu.edu/mythlore/vol35/iss1/7