Has anyone said “publication order, fer sure!” yet?
Honestly, reading them in Chronological Order only differs from Publication Order by shifting two books earlier into the series: pulling “The Magician’s Nephew” from its #6 slot and sticking it into the #1 slot, and pulling “The Horse and His Boy” from its #5 slot and sandwiching it between “The Lion the Witch and the Wardrobe” and “Prince Caspian”.
But I like publication order best, because that’s the order in which things get fleshed out, if that makes sense? Basically, you’re discovering the world in the same order that Lewis discovered the world. There’s a nice logic to it-- you start with the four Pevensie children; you stick around with them for a second book; you ditch two of them and bring in Cousin Eustace; you ditch the last two originals but bring back Cousin Eustace and bring in a new friend.
The last three books, on the other hand, are more about developing what-Narnia-is rather than the outsiders’ experience of Narnia. “The Horse and His Boy” is about turning to some other countries and cultures in that land, with only the very slightest connection to the four Pevensies at the end. And, of course, “The Magician’s Nephew” and “The Last Battle” are less about the characters, and are more like Narnia’s Genesis and Narnia’s Apocalypse. So, basically, “The Magician’s Nephew” answers all sorts of mysteries that cropped up earlier-- and who wants to read the solutions to mysteries before you even know there’s a mystery built up around it?