When Digory and Polly try on rings that belong to Digory's uncle, they pass magically through to other worlds. In the course of their adventures, a witch is released from her magical imprisonment, they watch first-hand as Narnia is created from nothingness, and Digory's mother is healed from her painful disease.
If you've read and enjoyed The Lion, the Witch, and the Wardrobe, then you owe it to yourself to read this "pre-quel". Apparently, Mr. Lewis wrote it after he wrote The Lion, the Witch, and the Wardrobe to explain a few things. So, even though it is not the first book he wrote, it is the "first" book of the Chronicles of Narnia series. In any case, it is interesting and well-written. I really liked finding out where the wardrobe and the lamp-post came from! It is a simple story but enjoyable if you like fantasy stories.