And thus did an Assistant Pig-Keeper become High King of Prydain. - Lloyd Alexander

"Once," he added, "you told me that the seeking counts more than the finding. So, too, must the striving count more than the gain."

Children's literature is considerably more functional than a good portion of adult literature. If I were cynical, I might say: Children's books are written to be read; adult books are written to be talked about at cocktail parties.
There may be more truth that cynicism in that statement. My impression is that many adult books are written only to shock the reader (a short term goal, since shock quickly turns into boredom) or as calisthenics for the author's ego.
On the other hand, children's literature seems an area where books function as they were meant to; where they amaze, delight, and move our emotions. We can respect and admire any number of current adult books, but I find it hard to love them.

On the level of high art, in their common efforts to express human truths, relationships, attitudes, and personal visions, children's literature and adult literature meet and sometimes merge, and we wonder then whether a given work is truly for children or truly for grown-ups. The answer, of course, is: for both.