Alan Jacobs passed along this fascinating little bit on Lewis's story:
My real criticism of this novel relates to a different matter. It is that it ends just when it is getting interesting. The Pevensie kids become the kings and queens of Narnia: King Peter the Magnificent, Queen Susan the Gentle, King Edmund the Just and Queen Lucy the Valiant. They grow to adulthood in this world, until, many years later, they chance upon the lamppost again, and tumble back into our world, no longer adults, now children. Only a few hours have passed on Earth, for all the year (decades?) they spent in Narnia. Then Lewis stops; but this is where the story starts, surely -- what would it be like to have an adult consciousness inside the body of a child? To have passed through puberty, and then suddenly to have the hormone tap switched off? You could hardly go back to you former existence; but neither could you expect to live as an adult. Would you go mad, or use your beyond-your-seeming-years wisdom to some purpose? How would you cope? Would you try to explain? Would you betray yourself, and reveal the Narnia portal to the world -- would governments attempt to exploit it? The psychological interest in the story begins at the end; but that's exactly the place where Lewis drops the bar down and ends things. Grrr!
I'm tempted to say that cultivating an "adult consciousness" is simply one of the many things that imaginative literature and play provide for children. That's a tough note to swallow, if only because for most of us what distinguishes the "adult consciousness" is simply (and perhaps exclusively) related to those "raging hormones" and everything they lead to.
But erotic attachments are not Lewis's theme, and as a result the adulthood that he depicts in the Pevensies is one unfettered by them. He writes that the adult Queens of Narnia were objects of male affection and pursuit, but is silent on whether such attention was reciprocated. And given they are hunting together at the end, it's safe to say it was not.
This subordination of erotic attachments become clearer when the ending of the book is put into relief against one of its potential sources: Shakespeare's Midsummer Night's Dream. Here's the High King Peter when they discover the lamppost:
"I know not how it is, but this lamp on the post worketh on me strangely. It runs in my mind that I have seen the like before, as it were a dream, or in the dream of a dream."
And here, of course, is the famous bit from Midsummer after the lovers are discovered: "Are you sure that we are awake? It seems to me that yet we sleep, we dream."
The textual parallel is only a hint (though one strengthened by the preceding dialogue in Midsummer), but the contexts of the utterances have their own antitheses as well: the four are siblings in Lion, while Midsummer's has its lovers. In both, though, a pair of men and women. And in Midsummer it is the lovers who are discovered by those on the hunt, while in Lion they are on the hunt themselves. But in both, it's precisely hunting that leads to the conclusion.
What to make of all this?
The concord in Narnia is not brought about by the resolution of sexual desire, as in Midsummer, but by transcending it.
And as such, Narnia affords the Pevensies an experience of adulthood that is limited in one key respect. But while it is no less adulthood for it, it more closely approximates childhood than Roberts seems to grant. I think of a line by Lewis's mentor George MacDonald: "There is a childhood into which we have to grow, just as there is a childhood which we must leave behind." Somewhat paradoxically, the imaginative experience of adulthood enables moves that transition along by deepening the experience of childhood (affected, as it is, by flights of imaginative fancy) and so enabling the possibility of adulthood. Even if that experience doesn't encapsulate all the freedoms and privileges we afford to adults.
Postscript: I offer all of this by way of exploration. It's a hypothesis, and by no means determinative. I'd be interested to hear critical feedback and questions in the comments, as I'm not sure I've put the thought out clearly enough. It is a new parallel to me (tonight!) and such things take me time to work out.