It's like the hole in the ozone layer, or starvation in developing countries - the millenium bug problem hasn't gone away just because everyone is fed up hearing about it. And given that the word "millennium" has been boring people by itself for years now, readers could be forgiven for approaching Millennium Shock with a cautionary lack of enthusiasm.

Which would be a pity, as it's rather good. The Y2K problem - as computing professionals have begun referring to it - still has the potential to cause catastrophic equipment failures the world over. It's an imaginative idea that the end of this century would provide the perfect opportunity for alien sabotage across the planet, paving the way for invasion - the anticipated widespread technology failures acting as perfect cover - and this is the basis for the story Justin Richards has constructed as a sequel to his popular System Shock. It features another meeting between the fourth Doctor and the older Harry Sullivan of that novel - and Harry must, by now, be completely fed up with the paranoia he has to suffer as a result of his superiors proving untrustworthy.

Although it's at least the third Doctor Who story to be set around this superficially significant moment, in this instance there's a strong dramatic reason for this - it's the pivotal moment at which problems caused by the millennium bug will become prominent - and surprisingly, there's no reference made to the fact that the Doctor is actually wandering around San Francisco, with not dissimilar aims, at the same time...

The main drawback may be a result of the novel's rushed production - it's rather distant, the reader is very much observing the events rather than being drawn into them, with a little too much reported speech in place of quoted conversations. It's almost impossible to keep track of who everyone is and how they fit into the plot, and the semi-disguised appearance of real political figures, including British Prime Minister "Terry Brooks", only emphasise that this isn't really happening. Nevertheless, and despite a lack of polish, Millennium Shock succeeds as a modest, entertaining thriller.