Of the most intriguing 40 Christian non-fiction titles published in the first half of 2016, historian George Marsden’s new book — C.S. Lewis’s Mere Christianity: A Biography — stands out immediately. Published in Princeton’s pioneering series, “Lives of Great Religious Books,” Marsden has written a biography about a book, and if that sounds boring, it’s not. Lewis’s classic has a backstory worth telling and Marsden has told it in one of the best books of the year.

When it comes to Amazon’s bestselling books in Christian apologetics, Mere Christianity has claimed first place ever since I can remember. The book was originally the product of a series of short eight-to-fifteen-minute talks delivered on BBC radio by Lewis during World War II, and delivered to an increasingly post-Christian British audience who now lived under perpetual fear of night bombing raids.

He gathered a listening audience of between 1–1.6m, which was big but not huge (the evening news update programs would draw ten-times that number). He pulled the short addresses off with great skill and imagination, but it was all met with mixed reviews in the British press, and generated an almost unbearable amount of fan mail for Lewis.

Marsden retells the amazing story of how God used one wartime intellectual, but also a novice apologist and lay theologian (CSL), to invest himself in the immediate medium at his disposal (BBC), in a dire time in world history (WWII), to produce talks that would become three separate books, then one book, that would be published and would spread globally in the 1950s, and then largely drop off and get forgotten during the sexual revolution in the 1960s (except at Wheaton College under the key influence of Clyde Kilby), and then would surge in the late 1960s and take wings in the 1970s — largely by the long-tail of word-of-mouth spread — leading to a swell of posthumous sales and popularity and eventually to Amazon’s top spot.

In the end, what makes Mere Christianity so powerful? All Christian non-fiction apologists will pay close attention as Marsden summarizes the key features of Lewis’s work (pages 153–188):

1. Lewis looks for timeless truth as opposed to the culturally bound.
2. He uses common human nature as the point of contact with his audience.
3. Lewis sees reason in the context of experience, affections, and imagination.
4. He is a poet at heart, using metaphor and the art of meaning in a universe that is alive.
5. Lewis’s book is about “mere Christianity.”
6. Mere Christianity does not offer cheap grace.
7. The lasting appeal of Mere Christianity is based on the luminosity of the gospel message itself.

A respected historian has retold a worthy story any Christian reader or writer will benefit from hearing. Like his biography of Jonathan Edwards, though shorter by 460 pages, Marsden has once again pulled off a masterpiece of history, in retelling the fascinating life of one of the most influential Christian books in the past century.