In ''2010: Odyssey Two'' Arthur C. Clarke has accomplished what few modern science fiction authors seem to be able to do. He has created a story that contains elements of both fantasy and classical science fiction on the grand cosmic scale, while maintaining a vivid sense of reality - staying true to the human realities of space travel, incorporating new facts gleaned from the 1979 Voyager space probes, and making believable scientific projections based on those facts.
At the conclusion of ''2001: A Space Odyssey,'' published in 1968, Clarke leaves astronaut David Bowman (reborn with the help of a large black monolith) floating above Earth, wondering what to do with his newfound powers over space and time.Meanwhile Hal, the self-conscious computer gone dangerously schizophrenic, circles a moon of Saturn in the spaceship Discovery. (In the current sequel, ''2010: Odyssey Two,'' Clarke quotes several passages from the book ''2001'' but follows the movie version of the story, in which Discovery orbits Jupiter.)
Beginning where ''2001'' left off, ''2010'' follows three major story lines: Bowman's fate, the investigation of the Jupiter monolith by the spaceship Leonov , and the rehabilitation of Hal.
The anticipated theme in Bowman's rebirth is one of the most intriguing in science fiction: Into what kind of being could Homo sapiens evolve? Clarke, however, bypasses the question and chooses to treat this part of the story as cosmic fantasy. Bowman has been reborn as a force field capable of manipulating human events. It is soon obvious that he is being manipulated in turn by the masters of the monolith, whose purpose and identity add mystery to the engrossing plot.
A pleasant contrast to the fantastical treatment of Bowman's superhuman exploits is the central story: a realistically drawn portrayal of the voyage of the spaceship Leonov. Clarke, author of 26 works of fiction and 25 works of nonfiction on space science and oceanography, presumably knows his astronomy, his space technology, and his orbital mechanics; and he doesn't compromise them to fit the plot. Rather, he uses his facts to give the reader a credible experience of space travel.
Also - Clarke's science fiction, as the art of making projections based on established fact, successfully creates such things as an amazing core for Jupiter and intriguing life forms beneath the icy crust of Jupiter's moon, Europa.
Only rarely does Clarke indulge in the kind of preachiness that keeps science fiction firmly locked within its genre. ''What shocking linguists we Americans are!'' says the central character, and he doesn't leave it at that. The story's opening nationalistic generalizations and conflicts are studiously anti-chauvinistic and unimaginative, hence disappointing.
As the story progresses, Clarke manages to work in some good characterizations: a sternly expert female Soviet Commander; a boisterous American engineer; the repressed, competent Bowman; and a self-effacing Indian computer scientist, who is frighteningly defensive about Hal. The computer's erratic personality adds several facets of suspense and interest, since its rehabilitation is held in question to the very end.
Even though Bowman and Hal are somewhat neglected and eventually shunted aside for the larger theme, Clarke's story drives on to an exciting finish in which the mix of fantasy and fact leaves the reader well satisfied with a book masterfully written.