Which set was that? The set that I have was by Collier Books (a division of Macmillan Publishing). I believe they were printed in the 1970s. At least the publication date on the individual books say 1970. This set consists of tiny, white books, topped with "C.S. Lewis" in black. Under that is the title. Then below that is an extremely colorful, '70s-esque cover image (in the one for The Lion, the Witch, and the Wardrobe, Peter and Edmund remind me of The Beatles from the Yellow Submarine movie). In a tiny arch above the image, it says "Book X of The Chronicles of Narnia." And then on the back, there's a little blurb about this book being like a passport to Narnia and encourages you to read them all. And then, there is a list and one-sentence description of each book.

So, yeah, which set do you have, and how old is it?