Summertime delving into adventure, mystery, computers, friendship, family life

This season's new books for young adults combine wholesome themes with a variety of entertaining scenarios. For mystery and adventure lovers, Raboo Rodgers has written Magnum Fault (Boston: Houghton Mifflin Company. 185 pp. $10.95. Age 14 up), a suspenseful account of two courageous teen-agers on an exciting mission in the Arkansas wilderness.

Jill Faraday, 17, is searching for her dad, a geologist who disappeared after a car accident. His last words to her indicated that something was wrong with the fault line. Cody Burke, also 17, has his own mystery to solve. An avid canoeist, he watches his beloved Patawa River suddenly cease flowing. Even Cody's friend and mentor, old Joe Tiotec, the last Patawa of his tribe, cannot explain this strange occurrence.

Jill and Cody are flung together by chance. Evading ominous pursuers, Jill, a skilled amateur pilot, steals a plane; Cody and his dog Riley are her unwitting passengers. When the plane runs out of fuel and crashes in the dense Patawa Preservation, it is Jill's determination and Cody's wilderness lore that enable them to survive.

When Jill finally locates her father, the mystery becomes more complicated. He has found the secret to the river's demise: Magnum Gas has been mining illegally over the fault, diverting the river, and endangering the whole valley. The teens must rescue Mr. Faraday and somehow stop operations before the Preservation is destroyed. Once again their quick thinking and resourcefulness save the day.

Rodgers has added a number of cliff- hangers that will delight readers. For a first novel, this is a skillfully constructed story that keeps the reader on the edge of his seat. The characters and the wilderness setting are well drawn, and the issue of social responsibility is an important one for youngsters to consider. Best of all, this is an adventure story that both girls and boys will enjoy.

Another adventure story combines the world of computers with the theme of social responsibility. In The Gadget Factor by Sandy Landsman (New York: Atheneum. 168 pp. $11.95. Ages 10-14), Michael Goldman, a 13-year-old math genius and misfit, enters college, where he has a difficult time adjusting. At college Michael discovers, what else, computers! He becomes more and more caught up in the world of the machine. ''It was more real than sitting in classes or trying to communicate with kids who looked at you like a freak or a munchkin.''

With his roommate, Worm, Michael invents the world's most elaborate computer game called Universe Prime, a detailed model of an entire universe. Surviving on donuts and coffee, disregarding sleep, calls from parents, clean clothes, and all their classes, Michael and Worm become co-rulers of Prime.

After reading an article by Prof. Terence Miller in the Weekly Science Review , Michael invents a series of mathematical formulae to create time travel in his alternate world. To their surprise, Michael and Worm discover that their formulae may actually work in the real world. The only problem: the concept as played out in Universe Prime results in the destruction of the universe. Could this happen in the real world too?

It's a dizzy rush to find Dr. Miller and avoid doomsday. In opposition to Dr. Miller, a college dean, and his irate parents, Michael is forced to make a moral decision that affects his own future and that of the world.

''The Gadget Factor'' will hold the attention of any youngster interested in computers and provides insight into the emotional world of the child prodigy. As Michael says, ''I began to get the feeling I was an exhibit at a science fair.'' With computer whizzes getting younger every day, many readers may identify with his problems.

Getting along with others, whether peers, parents, or siblings, is part of the growing process and a common theme in young adult literature. Two new novels deal successfully with this universal problem.

''When the world has come to an absolute end, it's hard to believe that people expect you to go on,'' begins Truth or Dare by Susan Beth Pfeffer (New York: Four Winds Press. 131 pp. $9.95. Ages 8-12). The ''end'' for sixth-grader Cathy Wakefield is a new school without her two best friends, Mary Kay and Francie. Desperate for friendship, Cathy goes about solving her problem in exactly the wrong way. On the first day of junior high, she spots Jessica, the most sophisticated and beautiful girl in school. Jessica lives in a spotless house and travels to Europe during the summer. Popularity, Cathy decides, means being Jessica's friend.

She sets out to join Jessica's circle. She goes places she doesn't like, hangs on Jessica's every word, and gives Jessica her phone number twice (Jessica never calls). Meanwhile, she rejects the friendship of classmate Libby Katz and doesn't return Mary Kay's calls.

When Jessica offhandedly remarks that Cathy lacks sophistication, her crusade intensifies. On advice from her older sister Cathy reads ''The Bell Jar'' (a sophisticated book), invites Jessica over for a salmon with raspberry sauce dinner, and considers changing her name to Catherine. All these ploys fail. Cathy can't get past Page 2 of ''The Bell Jar,'' plus she dislikes gourmet food. Worse, Jessica accuses her of being a tag-along.

Eventually Cathy realizes that friendship has been there all the time, not with Jessica, but with Libby, and that she had not been behaving like a true friend. ''There was a real good chance I was the awfullest person in the world, '' she concludes.

The story rings true as a chronicle of Cathy's painful struggle to find out what real friendship is all about.

In Which Way to the Nearest Wilderness (Boston: Little, Brown and Company. 166 pp. $12.95. Ages 8 to 12), Tricia Springstubb skillfully and humorously explores the effects of parental tension on all members of a family.

Eleven-year-old Eunice Gottlieb is a middle child, the sensible one who feels like a can opener (something useful and practical). She shares a room with her high strung, arty older sister, Millie the Pretzel, who's into yoga and Zen. They used to be close before Richard, Millie's zany boyfriend, came along. Now Millie barely acknowledges her sister's existence. Her younger brother Russell is sensitive and withdrawn. Arguments make him curl up like a poked caterpillar. Unfortunately, arguments - between Eunice's parents- are everyday occurrences in the Gottlieb household.

When Mom walks out, about twice a month, Mr. Gottlieb retreats to the basement to build perfect miniature houses (while their own shatters). Millie runs to Richard, and Eunice turns to the television for escape. ''I would shut this junk off, by then what would I do?'' Her Parent Radar, located in the pit of her stomach, tells her that things are getting worse. ''It was like being trapped in a recurring bad dream.''

In an attempt to find peace and order, Eunice discovers Thoreau's ''Walden'' and goes into endurance training: taking cold showers, eating bark (an acquired taste), and briefly contemplating giving up pastry. To finance her escape into the wilderness, she and best friend Joy start an unfriendly greeting card business, ''When You Care Enough to Send the Very Worst.''

In a crisis, Eunice, who has always taken her father's side, begins to understand her mother's complaints and sees that her sister and brother's behavior are means of coping with the tension that hangs over all of them, the fear of splitting apart. The Gottliebs realize that there are no fairy tale solutions, no happy-ever-afters. Being together and getting along requires hard work.

''Which Way to the Nearest Wilderness'' is a delightfully sweet-and-sour book that blends humor and sadness - no small achievement. Young readers are certain to relate to some aspect of Springstubb's portrayal and gain insight into their own family's dynamics