FOR EACH PROTAGONIST in this group of novels for young adults, facing up to a challenge is as necessary as breathing. For some, coming to grips with a challenge means passing another milestone along the road to maturity. For others, it's a matter of life and death. For Findabhair (pronounced "finn-ah-veer") and Gwen, the joint heroines of 0. R. Melling's The Hunter's Moon (HarperCollins, 173 pages, $16.95 cloth), however, the challenges come from all directions. Fantasy-loving Findabhair dares to sleep on sacred Irish ground and is stolen by the King of the Fairies. Gwen, her more practical Canadian cousin, sets out to rescue her with the help of a leprechaun in a battered Triumph and a businessman with red hair and freckles. What makes this story sing is the ease with which Melling alternates between fantasy and reality, making her readers, like her characters, "Comfortable with both." Add generous helpings of suspense, romance, humour, and atmosphere you could cut with a knife, and the result is a thoroughly enjoyable yam by an author with impressive command of her material.

The Prism Moon (Red Deer College Press, 165 pages, $9.95 paper) is the second book in a trilogy Martine Bates is writing about the adventures of Marwen, a young wizard-in-training who has inherited her father's magical talents but has yet to convince her compatriots that she is his true heir. She's also under constant threat from a mysterious rival who relentlessly pursues her and who specializes in evil spells by long distance. Unlike Melling, who writes within the tradition of Irish folklore and legend, Bates is free to determine all the rules in her fantasy world. With this much freedom it's tempting to be arbitrary, and Bates's habit of making her heroine suffer through countless trials occasionally produces an arbitrary, as opposed to inevitable, development in the plot. Perhaps her teenaged readers will be too much under Bates's own spell to care, however, if the following passage grips them as intended:

The victim lay upon the altar, her chest bared. Her mouth was wide open, and out of it came a long thin wail. With a knife a man slit open her breast and quickly removed the beating heart....The victim had time to see her heart beating in the hand of Maug, and to watch it quiver and pulse its blood over his hand and into her eyes and mouth before she died.

Meanwhile, Marwen watches from her prison window as this reader wonders why the heck, if she's a wizard's daughter, she can't figure out a way to escape. But all's fair in love and fantasy fiction, it seems.

Jeni Mayer's Suspicion Island (Thistledown, 176 pages, $7 paper) opens with a promising burst of R. L. Stevenson-style adventure but begins accumulating a familiar set of contemporary teenage problems by chapter three. Daniel, the 16-year-old protagonist, comes to visit his newly remarried grandfather on one of B.C.'s Gulf Islands and finds a ransacked, empty house, a hostile Native girl he suspects is on drugs, and a frightening neighhour he knows only as "Crazy Jeb." What has happened to Grandpa? Where is Grandpa's new wife? Who cut the telephone line? What are all those strange markings in the sand? How many rhetorical questions is it possible to cram into one short novel? In the process of solving all these mysteries and many more, Daniel makes serious headway into growing up and learns one very important thing: never get in a boat unless you're wearing a lifejacket. Except for those ubiquitous questions, this is a lively, fast-moving novel that should entertain young readers of both sexes.

In Laws of Emotion (Thistledown, 207 pages, $ 7.95 paper), Alison Lohans collects 11 short stories that deal with the more devastating of human emotions - love, grief, despair, frustration, jealousy, shame, pity, fear, anger, awe, In each story, a teenaged protagonist faces a difficult situation and finds a way to cope: for example, a girl whose boyfriend will probably not recover from a skiing accident learns that her own life must continue; a boy whose brother has been jailed for raping a girl at knifepoint discovers that his own girlfriend still loves him; a young girl who works on Saturdays at a nursing home overcomes her distress when a special patient dies, and decides to remain in her job. Though openly didactic, these stories have the merit of respecting turbulent young emotions and could conceivably be helpful to readers with similar problems.

Teenaged angst pales beside the challenges faced by 14-year-old Daniel of Frankfurt, Germany, however. The year is 194 1; Hitler is in power and is deporting Jews to Poland. By 1944, Daniel's mother and sister are presumed dead and he and his father are imprisoned in Auschwitz, where they experience unforgettable horrors. Daniel's Story (Scholastic, 136 pages, $4.95 paper), by Carol Maras, was written to coincide with an exhibit at the United States Holocaust Memorial Museum in Washington, D.C. Although Daniel is a fictional character, his story unsparingly recreates, for a new generation, the dreadful realities of Nazi Germany.

If we forget, we will once again be defenseless against evil. If we forget how bestial, how brutal ... clean, upstanding citizens became, if we forget, then we too could become that way,

Maras has Daniel say, in justification of a book that could give some of its young readers nightmares. This is strong medicine, to be taken with caution. Another kind of tyranny turns up in Ann Alma's Skateway to Freedom (Orca, 150 pages, $6.95 paper). This time the menace is the East German secret police, who threaten the futures of 11 -year-old Josie Grun and her parents in East Berlin. Fearing arrest for his liberal opinions, Josie's father plans the family's escape through Czechoslovakia into Hungary and Austria and thence to Canada, where his brother is established in Calgary. This gives Alma the opportunity to describe things Canadians have learned to take for granted wasting plastic and paper, for example, or accepting the view that, in economic terms, some are more equal than others - through the eyes of a newcomer. After a thrilling and dangerous adventure, Josie's most pressing problems soon become learning English and fitting in to a Canadian school. But Josie Grun is no ordinary girl. She has courage, and she loves to skate. Alma, who came to Canada as an immigrant herself and went on to teach school for 18 years in Armstrong, B.C., can empathize with the plight of young new Canadians. Josie and her parents are nicely rounded and sensitively imagined characters. It's a pleasure to make their acquaintance.

The same holds true for the fictional family in Kevin Major's Diana: My Autobiography (Doubleday, 136 pages, $12.95 paper). Doubtless seeking new worlds to conquer, here Major tackles writing in the first person as an 11 -year-old girl. He pulls it off very well, too, despite an irrepressible urge to soar with Diana (who is named after Princess Di and never forgets it for a moment) somewhere over the top:

I can't feel really happy living in a country where, no matter how intelligent you are or how much you study and practise, you can never get to marry a real prince. All you can ever hope to do is shake his hand and say, "Welcome, Sir. Have a nice visit." Then ten days later watch him fly off, back to the lucky girls who happen to be born English but wouldn't make half as good a princess as I would.

Captivated as she is by all things English, Diana takes up tennis and falls for the visiting Willard, whose accent is "straight out of Mary Poppins" and who could use a tittle tutoring in such Newfie pastimes as wading through a school of caplin and casting for trout from a canoe. This is a funny, clever story, enhanced by Major's ear for dialogue and his sly digs at Diana's novel-writing dad. Like Melling's The Hunter's Moon and Alma's Skateway to Freedom, it achieves a satisfying balance between significant challenge and convincing response.