THREE NEW FALL books for teenagers are refreshingly good, each in its own way, and all are free of the wonderful-kid/lousy- adult pattern we've come so tiredly to expect. Maybe there is a swing on the way that will take the category back to honesty -- it seems to me that Maureen Daly's Seventeenth Summer, maybe the first teenage novel, was pretty honest, creaky though it might seem now -- and that would be a blessing because it would free up story lines to deal, as the three here in question do, with issues more interesting than the generation gap.

Isabelle Holland's The Island is a first- rate suspense story, just implausible enough to make it exotic, and yet just possible enough to keep the reader happily involved. The heroine, Hilda, tells her own story of what promised to be a vacation in paradise but becomes instead a stay on the fringes of a figurative Hell.

She is sent by her father and mother to the small Caribbean island of Maenad (wonderful choice of name, under the circumstances) to visit a little-known aunt and an entirely unknown uncle. Their house and grounds on the highest island hill are filled with luxuries, but the island natives live in poverty. There are German shepherds being trained as attack dogs, Aunt Louisa is ill and stays mostly in her room, and Uncle Brace is as cold and hard as steel. And who is the other guest, the elderly, handsome John Gomez, who is so charming to Hilda?

The plot, closely woven, unfolds with admirable precision, but is too full of meaty details to be explicated here, and anyway, I don't want to give it all away. Suffice it to say that the roots of the mystery lie in the Second World War, and that the whole will satisfy your every desire for complicity, intrigue, romance, and, eventually, resolution.

Downtown, by Norma Fox Mazer, is another novel of suspense, but with less of a light-hearted core in that its resolution is always in doubt, even at the end. It poses a sad and interesting question: what has, what will, become of the children of the peaceniks? Pete Greenwood lives in the city of Winston with his bachelor Uncle Gene who is an optometrist by day and an active amateur actor by night. Pete has lived there for eight years. But his name is really Pax Martin Gandhi Connors, and his father and mother are in hiding after setting off a bomb in a laboratory where nerve gas was being developed. The lab was supposed to be empty. It wasn't. Two people, a scientist and a young assistant, were killed. Petewas bundled off to Uncle Gene, and his parents disappeared. All this is explained up front, and sets the stage for agonies of identity, trust, truth, and daily alarms: Pete knows the FBI is searching for his parents; he knows they will come for him, too, if they can identify him.

Woven into this principal plot line is a second involving Pete's romance with Cary, a foster child with agonies of her own, and to her he tells his story for the first and only time. Eventually the FBI appears, and Pete's mother turns herself in and is sent to prison. She sends for Pete. What are his obligations to a mother who put her ideas for world safety above the love of her son? Will he go to her? Mazer leaves it hanging. The characters here are real, unusual, and compelling, the situation painfully possible. I wanted a resolution, but even without one, this is a very good book.

And then there's Hilma Wolitzer's Wish You Were Here. The thing about Hilma Wolitzer is that she is a truly special writer. Her prose on any subject is pure delight. Not a whole lot happens in this novel, compared to the perils in those of Mazer and Holland, but who cares? Here we have Bernie Segal whose father is dead and whose mother is about to remarry. Bernie has two sisters -- Celia is rehearsing for the lead in a high school production of The Member of the Wedding, and Grace, a second-grader, mostly draws strange pictures with crayons and hoards her money. Bernie has decided to leave before the real and the stage weddings and go to live with his lonely grandfather in Florida, but to do this he must save up $99 for a special air fare, and must do it secretly because he's telling his plans to no one.

Through it all is a solidly convincing portrait of home and school life as seen through adolescent eyes, and Bernie's struggles to achieve his goal are touching and funny both at once. A surprise ending came as no surprise to me, but, again, who cares? This is a book that can be read over and over simply to savor the style.

I suppose it's useless to hope that teenagers know how fortunate they are to have writers like these working for them. But they are fortunate. It's a pity that most adults outside the field don't know it, as well. Why is it so hard to get kids to read when there are such good books available? Oh, well, these three, anyway, will surely find their audience.