While I first read this book in the mid-70s, I read it again to my wife a couple of years ago (we both loved it then as much as I did the first time). Most people know that C. S. Lewis was an effective Christian nonfiction apologist, using the tools of reason and logic to build the philosophical case for Christian faith. But he ultimately became convinced that an even more effective apologetic is available through the "truth of art," the instinctive and emotional appeal that stories exert -- especially the kinds of stories that draw on the deep, mythical archetypes of fantasy to illuminate the real universe. The Chronicles of Narnia, his classic fantasy series, was the fruit of that discovery, set in Narnia, a magical land whose world lies in another universe, in which magic works and time moves differently than it does here, and in which Christ is incarnate as the great talking lion Aslan. This first book of the series presents one of the most powerful symbolic literary presentations of the Christian gospel ever written. Although the intended audience, in Lewis' mind, was children (and his author's various direct addresses to the readers presuppose this), there is nothing invidiously "juvenile" about the quality of the writing; it can be enthusiastically appreciated by anyone who loves tales of imagination and adventure, fantasy and wonder; and the truths here, like those in Jesus' parables, are simple enough to speak to children but profound enough to challenge adults.

This is the "first" book of the series in the sense of first to be written (and usually the first to be read). However, The Magicians Nephew is a prequel which describes the creation of Narnia, and the origins of the White Witch and of the wardrobe that serves as a gateway to Narnia; Lewis himself recommended that this prequel be read first.