I would say read them in the right order.
There are seven in all and the first is ' The Magician's nephew'. It explains how the path between our world and Narnia was opened. I think it gets avoided because of the whole Aslan = God thing.
There is a definite progression through the rest of the books; with the possible exception of ' The horse and his boy'; and characters appear in more than one so if you read them out of order you might not get why an event or person is significant.
I still love these books and I'm 35.