IF YOU ASKED most adults why they don't read children's books, you'd probably hear, "Because I'm not a kid." And you'd get a puzzled look. But, in fact, a fair number of the new titles for young readers -- forget for a moment the classics that haven't been designated "all ages" for nothing -- could be enjoyably read by adults willing to put preconceptions aside. It's not, after all, a matter of lowering one's dignity: there are frequently novels on the best-seller lists which are far more simpleminded than the better juvenile fiction.

Swan's Wing, a superb and poignantly beautiful fantasy by British writer Ursula Synge, is a case in point. Originally published in England three years ago, it's being released in this country now under the guise of a children's book; yet it's far and away more subtle, more haunting and more affecting than any grown-up story I've read so far this season. In a word, it's mature. And since it makes you think and feel, while winding you in the coils of its strong, elegiac language, and since it teaches you something about life, what does it matter if the setting is a fairy tale world?

Actually, fantasy publishing is a pretty healthy sector of the industry, whether for kids or their elders, although much of the popular literature contains created universes of greater elaborateness than Swan's Wing. Here, one steps into a medieval landscape of stonecarvers, guilds, plagues, priests and cathedras, yet Arthur and Merlin are but a wander away, while, simultaneously, one of Grimm's tales has come to life. But the story line is a simple one, centered on a quest, and its elements, on the surface, aren't terribly complex. The 11th brother, the one with the swan's wing from the fairy tale in which the sister has had to free her enchanted siblings, seeks to become whole again.

Joining him on his journey are a devoted goose girl and a master mason, the latter a man obsessed with the idea of perfection. There are perils aplenty encountered, from an outbreak of pestilence to a dangerous countess who quite resembles Andersen's Snow Queen, but no way to break the spell appears. Without giving anything more away, I'd only like to mention that the ending is a stunner and that Swan's Wing is a philosophical fable that examines human desires and dignity, gracefully peeling back layers to get at things as they really are.

ANOTHER KIND of enchantment takes place in M.M. Kaye's The Ordinary Princess, a very merry modern fairy story by the author of The Far Pavilions. Here, a royal daughter -- Her Serene and Royal Highness Princess Amethyst Alexandra Augusta Araminta Adelaide Aurelia Anne, known as Amy -- is given at birth, by one of her fairy godmothers, the gift of "ordinariness." This means that while her six sisters are insipid beauties, Amy is spunky and cute. Sadly, though, that's not enough for her family or for neighboring princes who find Amy's freckles off-putting when they come riding into the kingdom to seek her hand.

So Amy, fed up with the situation, runs away and eventually winds up a scullery maid at the castle of a conveniently unmarried young prince, who himself is weary of the boring girls he's supposed to choose among. Enter romance, naturally, and M.M. Kaye makes the whole thing -- story, characters, charming pictures -- into a lovely light confection that could well turn into a classic.

Allan W. Eckert has also made enchantments an integral part of his uneven and rather unpleasant fantasy, The Dark Green Tunnel. In it, three children on a boat ride in the Florida Everglades take a wrong turning and pass through a magic turnstile into a world of gnomes, centaurs, talking animals, etc., all ruled by evil King Thorkin. We soon learn that two of these lost kids -- a twin brother and sister -- are actually long lost: they're the missing part of a prophecy that predicts the end of Thorkin's tyrannical reign. What's wrong with this book, however, is the startling and gratuitous violence that's spread throughout. Too many creatures both good and bad suffer frightful deaths, making as many corpses in The Dark Green Tunnel as in a kung fu movie.

There's no denying the bloodthirstiness of the young, but Eckert has certainly overcompensated, if what he wanted to do is avoid being namby-pamby. Also, it's fine to challenge a child's vocabulary, but words likeesoteric, crepuscular and nictitating seem a bit much, too. I'm a grown-up, after all, and I found this novel upsetting -- even if the little boy who's been fried right down to his skull gets to come back to life.