It seems every Christian tradition has tried to claim C.S. Lewis as their own, even the Catholics. His apologetics Mere Christianity and The Screwtape Letters were some of the primary literature recommended in my baptist upbringing. He was respected by the charismatics. The reformed quote from him all the time, even though he was nowhere near being reformed.
In short, nearly everyone loves Lewis, and seems to give him a pass whenever he says something that might not jive with their own theology or tradition. “Mere Christianity” (the concept, not just the book) has been a significant unifying force throughout Christendom in the past 50 years.
I believe part of the reason for his success was his intentionally fresh approach. This describes it well:
He [Lewis] was in fact not a theologian in any true sense of the word, bfor he did not set about an investigation of doctrine, but rather made hinmself an apologist, a defender of the faith in its full orthodoxy. He was largely ignorant of the work of modern theologians, and was proud of this ignorance, because he thought it helped him to avoid taking sides in any faction fights. ‘A great deal of my utility’, he wrote in 1963, ‘has depended on my having kept out of all dog-fights between professing schools of Christian thought’
-Humphrey Carpenter, The Inklings, p.175