ALL SCIENCE FICTION is contemporary fiction. The writer may ponder hard the prospects of non- renewable resources, political trends, and other curves on the futurologists' graphs, but his fiction will prove with the passage of years to reflect primarily -- sometimes solely -- the era in which it was written, like art forgeries which, decades later, inevitably betray the sensibilities of the age that actually wrought them. Sf works focusing on the advent of the 21st century such as Robert Heinlein's The Green Hills of Earth, Robert Silverberg's The Masks of Time and Russell Griffin's Century's End are set in wildly different versions of 1999 -- the projections of the early '50s, late '60s, and present day. Such books may tell us much of their age -- the famous Frederik Pohl and Cyril Kornbluth collaborations are as good a guide to the 1950s as anything by John O'Hara -- but fall short when enthusiasts make imprudent claims for their predictive value. The novels and stories considered this month, though their settings span the near, medium, and far future, are not about tomorrow but today.

William Gibson's Count Zero (Arbor House, $15.95) follows the phenomenal success of Neuromancer, the electric novel of high-tech lowlife that one critic characterized as "streetwise to the future" and which went on to win most of the awards in the field. In Neuromancer and several of the stories written over the previous few years, Gibson created a cybernetic world of the next century in which multinational corporations wield virtually sovereign power, and "console cowboys" plug into the Matrix, a nightlit world that embodies the relationships between data systems, to steal industrial data. Count Zero is set against the same background, and like the earlier novel and stories it centers almost immediately on betrayal and corporate intrigue.

In contrast with Neuromancer's linear plot, Count Zero runs on three tracks, which take up successive chapters before gradually converging. Each moves swiftly and engages the reader's interest in a grip that never lets go. Gibson's gift for breakneck pacing and his ability to create a compelling density of texture remain his major assets, for his skill in characterization still lags in the gray zone between stock figure and clich,e. The novel's familiar types include Bobby Newark, young would-be hotshot who becomes inadvertently involved with intrigues way over his head and is carried helplessly along to story's end, and Turner, an impassive corporate mercenary whose only code is his loyalty to whoever has hired him. Turner's purpose in the story is clearly to come in from the cold, and the question of whether he will perish from or survive whatever decisive act follows his recognition that a world of real feeling exists beyond his icy expertise provides the only suspense for his thread of the narrative.

Like his collection Burning Chrome (Arbor House, $14.95), Count Zero is redeemed by Gibson's audacity, his evident assurance (which sometimes skirts slickness), and his energetic, often dazzling style. The title story here is perhaps rather too similar to Neuromancer: amoral young cowboy past his prime engages in a reckless and highly illegal run he only half expects to survive and finds that success beyond his imaginings leaves a taste of ashes. The other stories share a surface glitter and sensibility that admirers have labelled "cyberpunk"; it is very much a sensibility of the '80s. Scientists at Work

GREGORY BENFORD and David Brin have also each won the Nebula Award for Best Novel, and their collaboration Heart of the Comet (Bantam/Spectra, $17.95) must have seemed a publisher's dream. Both men are practicing scientists, and an impressive amount of research went into the study of cometary phenomena and Halley's Comet in particular. The story of an international expedition to Halley's Comet in the next century seems to have everything: a large cast, a span of 80 years and billions of miles, love, conflict, and a succession of perils to face.

Yet while Benford and Brin are both experienced if unequally accomplished novelists, Benford-Brin writes like an amateur, and the result is something of a disaster. Quite possibly the novel was rushed in order to reach us soon after Halley itself did; a reference in the acknowledgements to "laboring under 'astronomical' deadlines" suggests that opportunism may have informed inspiration. Benford at least is a demonstrably punctilious writer whose novels often reach their final form only after successive stages of published expansion and revision. Heart of the Comet seems to have enjoyed no such consideration in composition, and the result shows.

In the mid-21st century the world's nations have begun to recover from decades of ecological disaster but are riven by a new controversy: a strain of genetically "improved" humans have been bred, called Percells after their creator. The Percells are widely discriminated against by the equatorial nations of the Third World, and the crew colonizing Halley contains both Percell and "Ortho" humans. When it is discovered that Halley contains life, which is "awakened" by the heat of the explorers' tunnels and begins to threaten the survival of the expedition, tension between Percell and Ortho spills over into mutiny and civil war.

This is material for a gripping story, but the execution is awkward and forced. Much of the first hundred pages is given over to exposition and long political arguments that are too plainly staged for the reader's benefit. A militant group of Percells, led by a Soviet crewmember, vows war against the reactionary Orthos, who in turn engage in a campaign of extermination. The novel's four main characters (American or American- educated Israeli) are left to hold things together with the foreigners acting so irresponsibly, and save the mission more or less singlehandedly. They also contribute a running romantic subplot that proves depressingly schematic: Lani loves Carl, Carl loves Virginia, Virginia loves Saul.

In the end the Halley life forms are tamed and become symbiotic beneficiaries of mankind. Saul, who helped create the Percells decades earlier and thus bridges the Ortho- Percell conflict, reacts especially well and is rendered immortal. As he is also the greatest mind on the mission and has by the novel's end filled the comet with his equally brilliant clones, he ultimately takes on the godlike attributes of a late Heinlein hero. Benford's protagonists have been showing this disconcerting tendency for a few years now. This, plus the concomitant trend in Benford's last few novels for his antagonists to be killed off in increasingly spectacular ways, prompts deep foreboding about the direction in which Benford and his fiction are going. Heart of the Comet ends on a note of visionary affirmation, but its triumphs seem unearned, its victories fixed.

A much more accomplished book is Gregory Benford's collection In Alien Flesh (Tor, $14.95). One reason it has taken Benford so long to publish a collection is that many of his best stories -- "Deeper than the Darkness," "Icarus Rising," "And the Sea Like Mirrors" -- have been reworked into novels. All of the stories here stand on their own, and show aspects of Benford's talent that do not really appear in his books. Several, such as the novelettes "In Alien Flesh" and "Relativistic Effects," possess that breadth of detail that suggests the germinal novel, but it is the short stories, such as "Nooncoming" and the madcap "Doing Lennon," that are especially welcome here, showing as they do Benford working as jeweler rather than muralist. Interestingly, the longest story, "To the Storming Gulf," seems the least finished, and Benford perhaps tellingly remarks that it may someday form part of a longer work. The Sea and Seasons

JOAN SLONCZEWSKI's A Door Into Ocean (Arbor House, $17.95) is set against a far future backdrop of interstellar conflict and galactic empire. Shora, the water-covered satellite of Valedon, has spent millennia of isolation following the collapse of an imperial hegemony. In the interim an all-female society has arisen, which practices a pacifist philosophy and lives on the ocean surface in complex harmony with its ecosystem, abjuring all non-organic technology. This culture, called the Sharers, is threatened when Valedon comes under the suzerainty of a renascent Empire, which intends Shora's subjugation. Two Sharers visit Valedon and bring back a youth, Spinel, to train as a kind of cultural ambassador, but war soon breaks out, and all three are caught between two cultures.

Slonczewski, who is a professor of biology, is at her best in portraying the rich world of Shora: the interplay between the society and the planet, as well as their ethical system and the ways in which it informs their culture and even language. Proximate worlds as the setting for "Western" and "alternative" cultures have been used in sf before, most notably in Ursula K. Le Guin's The Dispossessed, to which this novel bears a temperamental affinity. Like Le Guin, Slonczewski is better at portraying the culture that clearly holds her sympathies than its antithesis, and the encroaching Valans unfortunately resemble the neo-medieval galactic empires of unreconstructed space opera, with imperial garrisons and aristocrats bearing portentous titles such as Lady Berenice of Hyalite or Talion the High Protector of Valadon. Sensitive and often passionate, A Door Into Ocean is marred by the genre stereotypes and plain bad writing Slonczewski lapses into when her attention is off her real subject. Her portrayal of Shora is affecting, perhaps even memorable, but should have been shorn of its pulp entanglements, especially since the author's heart was plainly not in them.

After the magisterial Helliconia trilogy, Brian W. Aldiss' Seasons in Flight (Atheneum, $10.95) may seem a very small book, but these fable-like stories, many of them contemporary fictions with a touch of strangeness about them, address questions of the human condition with a refreshingly deft and sure touch. One or two could almost be set in Helliconia, but all manage to strike a perfect balance between the universal and the particular without need for reference to larger fictive contexts. Admirers of Aldiss' grander works, or of the unassuming short story, will welcome this book, which speaks to readers of today but will still give pleasure tomorrow.