Nicky The Magician's Nephew was the first book I've read, since it's like the prequel of the series. I prefered to read about the beginning of Narnia first. It made more sense to me, but it's really up to you. The Magician's Nephew is only oddball in the order, the rest of the books are in the same order. Hope this helps
Emma Greenspan I recommend reading it in chronological order, because The Magician's Nephew shows the start of Narnia, and gives more background information for when you read The Lion, The Witch, and The Wardrobe.