The tales had to be read by children before people realised that they were meant for grown-ups

From Anthony Lawton's site, Rosemary Sutcliff, is this article by Sutcliff on Kipling. Well worth a read.

Sutcliff has these interesting observation's to share on the nature of the challenge when trying to parse an author's works between adult and child.

But before going further with this somewhat random 'piece' on Kipling for Children, it might be as well to try to decide which of his books are in fact for children, and the moment one begins, it becomes perfectly obvious that the thing can't be done. There is no clear demarcation line. All one can do is to make a personal choice and give personal reasons and opinions, and apologise in advance to anyone who disagrees.

The Jungle Books, The Just So Stories, Stalky and Co., Puck of Pook's Hill and Rewards and Fairies immediately leap to mind. But of the Puck books, Kipling himself says in his Autobiography, "I worked the material in three or four overlaid tints and textures, which might or might not reveal themselves according to the shifting light of sex, youth and experience. The tales had to be read by children before people realised that they were meant for grown-ups". On the other hand, two of his full length novels, Kim and Captains Courageous originally intended for grown-ups, have always been read and loved by children, for, at least so far as these two books are concerned, Kipling belongs to the select company of writers - R. L. Stevenson, Rider Haggard and John Buchan are three more - whose books, written for adults, have been taken over by the young. How and why this happens to some writers is a mystery. I have seen it attributed in a recent T.L.S. article, to "A pocket of unlived childhood" somewhere in the innermost recesses of the author's being, and if, as seems quite possible, this is the answer, odd to think how much we who loved Kipling's adult books when we were children, and love his children's books still, may owe to the six miserable years of unlived childhood he survived under the shadow of The Woman, in the House of Desolation at Southsea.

She comments on the nature of the attraction of Kiplings' tales to a young child.

I was something under six when my mother first read The Jungle Books to me. They were my first introduction to Kipling, and perhaps for that reason, they have an especial potency for me. From the first, I had an extraordinary sense of familiarity in the jungle; I was not discovering a new world but returning to a world I knew; and the closest contact I ever made with a "Story book Character", I made with Bagheera, the black panther with the voice as soft as wild honey dripping from a tree and the little bald spot that told of a collar, under his chin.

The Just So Stories, Kim, and Puck of Pook's Hill, must all have followed soon after; at all events I have no clear memory of first meeting them, nor of a time before they were there, a time without the crowding delights and many-coloured over-spilling riches of Kim, on which one can get drunk as a bee among horse chestnut blossom; without the strong magic of The Just So Stories (no one understands better than Kipling did, the importance of incantation, the exact repetition of the word pattern until it becomes ritual "You must not forget the suspenders, Best Beloved" to all primitive peoples, including children); without Sir Richard Dalyngridge, that Very Perfect Gentle Knight, and the three magnificent "Roman Wall" stories of Puck of Pook's Hill which first, as it were, planted Roman Britain in my bloodstream.

Finally, she also comments on the challenge of that increasingly large number of children whom today we call third-culture kids, having to navigate, as did Kipling's characters between multiple loved cultures.

I did not in the early days, of course, see what any of these books were really about. I did not see that under the superb tale of adventure, Kim told basically the same story as The Jungle Books - of a boy belonging to one world, thrown into and accepted by another, and faced in the end by the same unbearable choice to be made between world and world, nor how much the story had to tell about the nature of love and the soul of Man.