C.S. Lewis, The Magician's Nephew

Perhaps the popularity of Narnia comes from Lewis having just the right sort of imagination. So:

Just beside them was a little, very dark-wooded tree, about the size of an apple tree. The leaves were whitish and rather papery, like the herb called honesty, and it was loaded with little brown fruits that looked rather like dates.

This is what one gets by planting a piece of toffee in the soil of Narnia. It would have been easy enough to say, "toffee tree" and be done with it. That Lewis decides to imagine the tree as a whole, bark and leaves as well as fruits, is rather typical of his powers of conception. The taste of allegory is here too of course, honesty and apples, but it is not Pilgrim's Progress (or Regress). And it perhaps is why these books reach an audience beyond those poised to accept the theology: by offering the details, Lewis offers a theology embodied in something that feels like life, if hardly realism. It is not so much that the moral can be discarded by those who disagree, but perhaps overlooked, as one politely nods at the eccentricities of an evangelical guest even though one would not invite in to tea the traveling evangelist.