If Marco Polo hadn't existed, the authors of children's books would almost certainly have invented him. His adventure was ideal fare for juvenile literature: the young boy who traveled the length of the known world, met all dangers, became the trusted friend of the great and dreaded Mongol emperor Kublai Khan--and returned to tell the tale. On his way home, he wrote his own book. The Venetians, blind to a good story when they saw one, hounded poor Marco even on his deathbed. He stuck by his facts to the end. Asked to take back just the parts that weren't true, he sighed, "I have not written down half of those things which I saw," and died.

But if half of those things were true it was an adventure, and these three books ought to excite the young reader. (None is a book for kids of all ages.) Elizabeth Levy's, whose publication coincides with the upcoming "television spectacular"--as it says on the cover--is a well- told story of Marco's 24-year odyssey. It contains mostly color photographs of such as Burt Lancaster (Pope Gregory the X), John Houseman (the Bishop Patriarch of Venice), Leonard Nimoy (Achmet, the Khan's regent), as well as spectacular--no kidding --Ektachrome vistas of Mongolian steppes, comely Mongol ladies standing by their yurts, a lamasery, scenes of imperial life within the Forbidden City, battles fought in bamboo forests, and torch-lit processions along the Great Wall.

The writing is good and instructive, full of dramatic dialogue, and probably right for the 7-to-11-year-old set. Parents will have a chance to refurbish their own vocabularies, in case they've forgotten what a lamasery is.

With photographs as vivid as these, prose, no matter how good, plays second fiddle. But kids who fasten on Levy's writing will come away with memorable reading moments and new perspectives, such as when Marco presents the Khan with the crucifix he and his uncle and father have brought with them--at considerable effort --from Jerusalem.

"Strange," murmured the Khan. "Yours is the only religion that has turned an instrument of death into an object of beauty and devotion."

This is a numinous proposition for the young mind, but gently and gracefully conveyed. Christianity, incidentally, is no seamless garment here: Marco watches a troop of amok Crusaders stomp a few Bedouin just for the hell of it.

"Father!" cried Marco. "How could men of God, Crusaders, butcher women and children?"

"They're just men, Marco. . . . There's no war as bitter as a religious war."

Another nice moment comes when Caidu Khan, a loner Mongol chieftain who thinks thrones and palaces are a bit, well, un-Mongolish, tells Marco why he's staying put on the steppes: "To settle is to perish. If we are given borders, we die."

There are many of these vignettes, anecdotes and encounters, and early on in the story, Marco begins keeping the journal that will become his book. This may not be lost on the young, reflective reader, who may be subliminally encouraged to start keeping one of his or her own.

The advantage of the Gian Paolo Ceserani Marco Polo, aimed at the same, or perhap at a slightly younger age group, is that its prose and illustrations leave a little more to the imagination. The illustrations by Piero Ventura let the reader inhabit a mre fantastical world than the one of still photographs from a movie set.

The text is embedded with images that might stimulate a child to think in metaphors, even though a few more years of English Comp will pass before he or she understands what a metaphor is. Cities "rush out to meet ships coming into port"; Marco traverses a "vast, sandy emptiness" of a desert.

The prose suffers a bit from the translation from the Italian. There are scattered references to "the Polos" (try to imagine Mr. and Mrs. Odysseus). But the translation also works a kind of quaintness. Mongols, we learn, "would eat even cats, dogs or rats--if they were low on larger animals."

This is a beguiling little book, full of enchanting details, such as the astrologers Kublai Khan kept on his roof all the time to chant away the storm clouds.

The Adventures of Marco Polo, by Demi, is, I'd guess, for 3- to 6-year-olds. The text probably doesn't exceed 150 words. Marco's voyage is related mostly by pleasantly cluttered maps showing what he saw along the way: "Holy Oil...Dangerous Robbers . . . Sheep with thirty- pound tails . . . Bleached bones of travelers who didn't make it . . . Yurts . . . Man-eating, savage Sumatra."

Horses are pink, sharks are blue and menacing as guppies, and warriors look only slightly discomfited as their heads are hacked off. Perfect for bedtime reading. Children learn about death too soon. Don't blame Demi. If Johnny is lucky--and historically blessed--he may never find out how much it does hurt. There are Soviet gunships out there now, and somewhere in those traveled sands of Iran the wreckage of Desert One.