For some reason I started with The Last Battle, but couldn't get through it. Of course, not being Christian, I missed all the symbolism of that book, and all the books. Never begin a series book with the word Last in the title. Eventually I got found my way to The L, the W. and the W and read the first four Narnia books in the right order (of publication, of course) and got to The Horse and His Boy very late. The Silver Chair was my favourite for a while. Maybe I identified with Lucy. Ultimately, I loved The Magician's Nephew the most. The world between worlds seemed quite believable to me - it still does. Perhaps that's why I never learned to dive. You can be oblivious to the Christian symbolism and be totally taken by these wonderful books.