Just about any list of the best Christian books in the English language, of course, will include at least one Lewis title. In fact, when Christianity Today magazine asked more than 100 Christian writers and leaders to rank the most influential religious books of the 20th century, they named Lewis’s Mere Christianity No. 1 by far—which explains why readers have purchased the around 18 million copies of the book. And Harper Collins, which distributed some 10 million in unit sales since it acquired the rights to most of Lewis’s titles in 2001, reports more than 150,000 copies of Mere Christianity sold in the past year.

But even those numbers seem small compared to the more than 100 million copies (in at least 30 different languages) of The Chronicles of Narnia series sold.

And Lewis’s stories seem just as comfortable in Hollywood as they are in a corner bookstore. In recent years, three stories of the Chronicles of Narnia appeared as major film adaptations, with a fourth in development. And other films based on his life and works have materialized, too—such as Shadowlands, which casts Anthony Hopkins as Lewis and tells the story of his marriage to Joy Davidman, and a forthcoming film version of The Great Divorce, currently in the development stage.

Lewis’s works also appear onstage: Shadowlands began as television film and later turned into a play, and the theater production of The Screwtape Letters will continue its current tour in California later this month.

Traces of Lewis even appear in the works of other writers. Most significantly, he helped Tolkien finish perhaps the best work of English literature from the century, The Lord of the Rings; McGrath calls Lewis the “chief midwife” to the stories. Another biographer suggests that J.K. Rowling’s Harry Potter series includes seven volumes as a kind of homage to the Narnia stories. Rowling’s character Dudley sounds and acts like Lewis’s Eustace Scrubb (from the Chronicles of Narnia series), and in an interview with the Sydney Morning Herald, Rowling said she found herself “thinking about the wardrobe route to Narnia when Harry is told he has to hurl himself at a barrier in Kings Cross Station.” Lewis’s work also shapes, axiomatically, the stories of Christian writers like N.D. Wilson (also the screenwriter for The Great Divorce adaptation) and Andrew Peterson, and has also influenced writers like Lloyd Alexander—who said, “In our times, every fantasy realm must be measured in comparison with Narnia.”

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One of the few men who did attend Lewis’s funeral was the English theologian and philosopher Austin Farrer. In his eulogy that day, Farrer effectively described the combination of logic and emotion—of fact and imagination, of prose and poetry—that made Lewis’s writings resonate with many demographics of readers: Farrer said, “There lived in his writings a Christian universe that could be both thought and felt, in which he was at home and in which he made his reader at home.” In other words, readers found—and still find—that Lewis narratives both answer intellectual questions and satisfy spiritual longings; Lewis demonstrates the importance of images and stories for the life of faith, without forgetting the necessity of reasoned, coherent belief, as well.