TO GET SOME UNDERSTANDING of the Dream Archipelago, it is perhaps worth noting that the Torquis island group can be found at the coordinates 44^oN - 49^oN and 23^oW - 27^oW, while the Torquils island group is located at 23^oS - 27^oS and 44^oE - 49^oE. There is also an island group known as the Torquins — though, since nobody has visited this group, it may not exist.

If that suggests that the Dream Archipelago is geographically and ontologically uncertain, a place where reality itself is unreliable, then you have come some way to understanding the playful undermining of our certainties that is the overwhelming characteristic of Christopher Priest's latest fiction, which recently won the British Science Fiction Association's award for best novel of 2011. Though to call the book a novel is only to use the least unreliable of any number of terms that could be applied to this complex and ever-shifting work.

When Christopher Priest began writing about the Dream Archipelago in the late-1970s the world-girdling archipelago was clearly an avatar of the Greek islands, which were just then becoming generally affordable for British holidaymakers and had already acquired a reputation for hedonism and sexual licence. This reputation is reflected here, for instance, in the erotomane laws on Torquil. In Priest's stories, collected in The Dream Archipelago (1999), the Dream Archipelago separated a cold northern continent whose technologically advanced nations were locked in a perpetual war, and a largely uninhabited southern desert continent where this war was mostly fought out. Between the two land masses lies a chain of islands so profuse that no one has a clear idea exactly how many there are. The islands of the Dream Archipelago represent the unease of neutrality, politically, morally, socially, and sexually. They are places of escape, particularly for deserting soldiers, and yet many of them turn into a trap in themselves; they are places of sexual freedom, but the price of such freedom is often death. The sexual allure that constantly draws visitors to the islands has a vicious side; the stories consistently render desire as threatening and generally fatal.

The psychosexual dramas played out in these stories were transformed in what many consider to be Priest's finest novel, The Affirmation (1980), in which the nature of identity is undermined and reconfigured. The islands become a place not so much of sexual or political liberation as of an escape from oneself, a place for reimagining one's own identity. At that point he stopped writing about the Dream Archipelago, though there were references to it in The Quiet Woman (1990), and later novels such as The Prestige (1995; the source for Christopher Nolan's 2006 film) and The Separation (2002; winner of the Arthur C. Clarke Award) continued to explore themes previously laid out in those stories. Recently, however, he has returned to the Dream Archipelago in a number of short stories, and now there is another novel.

The Islanders is as different from The Affirmation as it is possible to be and yet still retain that sense of shattered identities, unstable realities, the combination of allure and threat, and above all the willingness to challenge and experiment with...