Planet Narnia, by Michael Ward, provides a key to the seven books. They each represent a Middle Age heavenly body. Voyage of the Dawn Treader is the sun book. The Silver Chair is the moon book. The Last Battle is the Saturn book, where everything dies. When I listened to and read David Icke talk about Saturn, it seemed to tie in with this book. Look deeper into Lord of the Rings, by Tolkien, and again you can see Saturnine connections, particularly with Sauron and the ring.