Science fiction: it spooks, startles, and awes; J. O. Jeppson's galactic novel stretches readers, lurches from wonder to wonder The Last Immortal, by J. O. Jeppson. Boston: Houghton Mifflin Company. $9.95.

Is science fiction an infinitely malleable form? Can one successfully stretch the imagination through time, space, and dream without any limitation and still keep the reader's suspension of disbelief willing? Can one mingle high jinks and philosophy and still be taken seriously?

Many science fiction novels call forth these questions, but few to the degree of J. O. Jeppson's second novel, "The Last Immortal." Its setting encompasses two alternating universes, its time span billions of years. Surely this is one of the most unimaginably gigantic settings ever attempted.

Questions of dimension are often present in science fiction novels. In judging them, one asks if the scale is useful to the vision of the book. The old E. E. "Doc" Smith space operas, which commute among planets like driving downtown, form lighthearted entertainment; in them space is erased for the fun of it. Isaac Asimov's Foundation trilogy, on the other hand, conveys a sense of galactic enormousness that permanently enlarges the awareness of its readers. But Jeppson's novel has expanded space so far, and so casually, that it may well have lost meaning.

Great stretches of time are also common in science fiction. Again the trick is to provide the reader with aids to his vision of the vastness of this dimension. Joe Haldeman's "The Foreever War" explores the relation of time and space in an intricate and intriguing way, enriching the reader's sense of both dimensions. In contrast, Jeppson obliterates both. When, for example, her central figure, a robot older then our known universe, exchanges literary quotations with his companions a billion years hence, he limits himself to writers in English between Shakespeare and George Orwell. How real do these eons seem?

Using devices from other science fiction novels is common in the genre, as well. Generally, writers limit themselves to a few. But in "The Last Immortal" we find Asimov's laws of robotics, Cordwainer Smith's mutant cats, Anne McCaffrey's sentient space ship, Arthur Clarke's use of mythological creatures as actualities from somewhere else, alternate universes like those in "The Gods Themselves," the robot in love with a girl from "Barbarella." At times this novel seems an anthology of favorite science fiction devices.

It is also common in the genre to arrive at some point at which verbal prestidigitation is needed to dazzle the reader into accepting a quasi-scientific explanation so the story may move beyond our technology. This is great fun, and whole novels are built around these explanations. But in "The Last Immortal" at times the rate at which such inventions occur is dizzying, the narrative lurching form wonder to wonder.

There is the matter of proportion, too. Must one evoke whole universes to accomplish limited ends? The good guys do win big in "The Last Immortal." But then they curiously obviate the purpose of their struggles by inviting evil into the new universe they have inherited.

Jeppson's attempt seems to have been to write the greatest unlimited, intergalactic novel. Without question, this attempt will strecth her readers in many ways.