Evangelism is an extraordinary task; it's what God uses to bring people from death to life. But it has always been difficult. C.S. Lewis was used by God in the conversions of countless people, from friends and acquaintances in his own lifetime to modern-day readers of books such as The Chronicles of Narnia and Mere Christianity (the most influential Christian book of the 20th century). As Tim Keller comments, "C.S. Lewis was incredibly skilled...