We got the Narnia books for our kids when they were little. This will sound ridiculous, but in our Jewish household, the Christian part went right over our heads. The kids still liked them.
Aslan doesnt really make it plain that he is Jesus until the Last book. The christianity is there it just doesn't scream at you. It is more the attitude and morals that stand out.
Sam, you've hit the nail on the head. they're STORIES, and darn good ones. And while there may be allegories, etc within a work of fiction, more often than not it is not necessary to acknowledge belief in the second meaning, so to speak. In fact (as you point out), if you aren't concerning yourself with it - for whatever reason - it may not even jump out at you at all. And it sure isn't central to the work's quality.
Same applies to the Potter books, the Da Vinci code, etc.
To be sure, one can walk through life looking to nitpick anything into something blasphemous to them. But what a miserable way to live.
If you are living your life as you should, then reading a simple book isn't going to damn you to an afterlife of fire and brimstone. No matter what the hysterical group of the day would ram down your throat.
LOL I never ever as a kid thought of them as "Christian" books (I'm Jewish too). It just flat never occurred to me.
*shrugs*