The fact that I rarely read science fiction from choice doesn't prevent me from having an opinion as to what constitutes a good sci-fi novel. Quite the opposite. The best science fiction, I believe, needs many of the same ingredients as any other kind of fiction: compelling plot, sympathetic characters, realistic dialogue, elegant descriptions. In addition to these, it requires an important extra element: the capacity to stimulate thought, to cause the reader to ponder on aspects of everyday life which we take for granted, to look at technology in a new light.

Duncan Hunter's A Martian Poet in Siberia is just such a book. Its thesis is this: a group of "settlers", little more than children themselves, having grown up in a Martian colony, are given the unenviable task of attempting the repopulation of the mother planet, an Earth wiped out by the impact of a massive asteroid some time in the 23rd century. Their "return" has a triple unfamiliarity about it. The restricted life they know, first under an artificial dome in the Martian settlement and then for the long months of inter-planetary travel, contrasts not only with the Earth on which they arrive but also with the Earth they have learned about in their lessons. They are both coming home and leaving home permanently. Throughout their development as a community, they encounter random factors that can help or hinder their progress.

Ironically, it is through their accidental discovery of two survivors, an elderly couple with a knowledge of earth magic, that the newcomers come by the technology which enables them to make something of their surroundings. The coming together of the old and the reformed planet, the well-established and the newly-formed communities, are an object lesson in tolerance and receptivity to change.

Duncan Hunter writes with a great facility, his prose fluent but powerful, poetic yet unpretentious. His characters are brought to life, less through their own words - the narrator, Han, is their mouthpiece when it comes to communicating with the reader - than through their unspoken hopes and fears. They are of mixed ethnic origin, probably the healthiest way to kick-start Earth's new population, though the reasons for their selection are not specifically stated. This is one of many unanswered questions I was left with at the end of the book, and I could have wished for another thirty pages or so, just to dot the 'i's and cross the 't's.

That brings me back to my earlier comments. Good science fiction must, almost by definition, leave a few questions open. It would be too easy to invent some device for resolving each difficulty that arises out of the basic premise, to create a technological solution for every problem. This would be no more realistic than are the Martian colonists' expectations of their future on Earth, and an author who falls into such a trap need not bask in self-congratulation at having been clever enough to find a way out of every potentially tricky situation. The questions arising from the all too believable scenario of Mr Hunter's post-holocaust Siberia with its scattering of disorientated humans range from the practical to the spiritual. They are not there to be answered.