ONE OF the major differences between reading science fiction in the '50s and reading SF (an all-encompassing acronym meaning science fiction, speculative fiction, speculative fantasy, speculative fabulation, etc.) in the '90s has to do with a complex rearrangement of genre expectations and attendant formalities. As postmodern writing has shifted towards a difficult flattening and fragmentation of character, and has often used borrowings from pop genres to do so, some of the best writers in the mystery and SF fields have carefully deepened their work by adapting the basic aspects of literary realism. Some writers always tried to do so, of course, and one of the few in the science fiction ghetto to do so well was Theodore Sturgeon. Robert Charles Wilson has obviously learned a lot from Theodore Sturgeon, and I mean that as a high compliment. He has the same generous compassion toward people, especially the ordinary ones, and he tells stories that maintain their human dimensions no matter how awesomely immense the science fictional "given" of their narratives might be.

In The Harvest, that given is overwhelming: a magisterial yet subtle new twist on the theme of powerful visitors from outer space. In a huge artefact that hangs in the western sky for a year and generates mass fear everywhere, "The Travellers," a whole world of sentient beings who have chosen to become a single yet multiple entity in order to explore the cosmos, take cognizance of an ecologically deteriorating Earth. But we team this only after Wilson presents the various responses of a cross-section of ordinary humanity in the small town of Buchanan, Oregon. When the powerful entity sends huge blocks to all the major cities of the world, nothing can stop them: compared to us, they are like gods. Benevolent gods, it seems, for they then offer humanity a covenant. In a tong sleep imposed across the whole world, they ask each individual, Do you want to live forever? Wilson establishes the morality of the offer by indicating that the question touches, even seems to come from, the deepest centres of self and being. To be able to answer either way, one has to confront, accept, and in many cases forgive one's self. The experience, perhaps especially for those who answer yes - an overwhelming majority of humanity - is religious in all the ways we can measure.

But one in ten thousand refuses, and some of these, especially Dr Matt Wheeler, are the focus of the rest of the narrative. As the eight or so people of Buchanan who refused join together, we learn their different reasons, how well they adapt to the no-longer-human (as they see them) others and to the new condition of Earth, and how some few entertain ideas of destruction in their paranoid rage. Wilson does a good job of investing his ordinary characters with meaning and dignity, and he also suggestively shows some of the new humans, the more than human (to borrow the title of one of Sturgeon's most famous novels), slowly growing into their new being as members of a mental and spiritual holistic community.

As the trans-human entity slowly takes form, it literally turns Earth inside out to build a new artefact - an interstellar vessel vast enough to house all the minds of Earth and many bodies, as well as all the physical memories of the home planet it will need during its eternal voyage of discovery. This huge artefact takes shape in Wyoming, digging deep into the planet's core to find the materials and fuel it will need to blast free of Earth and escape the solar system's gravity. Meanwhile, as the new humanity slowly takes over running the Earth from the Travellers, it debates what to do about the recalcitrant few. In certain areas, "Helpers" can provide all the people need, and most of them are subtly herded there; but a few, including one old man Wilson makes us like for his stubborn curmudgeonliness, insist on living beyond the boundaries of these "edens." Wilson manages to gather the many strands of his narrative together at the end to evoke SF's particular kind of scientific transcendence, and he does so by never losing sight of the mundane realities of his central characters.

We are brought back to the generic paradox I pointed to at the beginning of this review: in this kind of SF, the sense of wonder is achieved through the careful craft of realism, through sneaking up on giant wonders through the perceptions of mainly normal, quiet, ordinary people. Wilson's grasp of the contemporary realistic mode, the kind of writing associated with Anne Tyler, say, is acute, and I intend the compliment implied in this comparison. Some readers might ask why he writes SF, then, but it is precisely his ability to ground his speculations in a shared sense of "the real" that marks him as such an interesting SF writer.

The Harvest is a satisfyingly complex, emotionally engaging novel. It takes its time, but it slowly and surely hooks the reader through the power of its characterizations and the complications of the many encounters among the various figures who inhabit its landscapes. With each new novel, Robert Charles Wilson adds to his reputation as one of the best SF writers of his generation.