In October 1945, C.S. Lewis wrote a slightly grumpy reply to someone asking him to do a book on Christianity, in plain language, specifically for workers. Since giving a series of wartime BBC lectures on the faith's basics, Lewis had become a kind of Christian Answer Man, and frankly, he had other ambitions and projects. "I am nearly 47," he complained. "Where are my successors?"
"It's interesting," says Alan Jacobs, author of The Narnian (HarperSanFrancisco), a new Lewis biography, "that 60 years later, nobody has really turned up." Lewis, whose day job was Oxford medievalist, did eventually get around to other work,...