Yea, it's somewhat of a hard one with Narnia.

The written order makes more sense, in terms of exposition etc. - but the Magician's Nephew is just way cooler overall, and it doesn't hit you over the head with Christian allegories right away... that is, by the time you get to the horrendous "creation" of Narnia, and the Eden allusions, you've already been lured in with cool magic rings, flying through space between worlds, a world where everyone's a monster, and dead, Jadis wreaking havoc around London, the crazy scientist cartoon - and the unbearable Narnia chapters just kinda flow from there.

Lion&Witch just starts off as this cheesy fairytale adventure, so it may not make for the best first impression :)