In Vinge's vast vision of a universe in which different zones of space impose their different constraints on technological development (in the 'slow' zone, faster-than-light travel is impossible but other zones have no such restriction), a long dormant and evil power is accidentally released with devastating consequences. The only potentially effective counter-measure to this Blight sweeping through galaxies lies with two children marooned in an alien world, medieval in its civilization, where the dominant creatures, the Tines, come from a dog-like species that only gains its intelligence when it combines in packs. A mission to rescue the children and take possession of the counter-measure, led by an enhanced and millennia-old human named Pham Nuwen, races across space, pursued by all those who have a vested interest in the spread of the Blight. Meanwhile, on the planet of the Tines, the children are caught up in a power struggle between two rival clans.

Vernor Vinge is a mathematician and computer scientist who taught for many years in San Diego State University and, outside the SF world, he is well-known for his ideas about the future growth of technology and what he called, in an essay published only a year after A Fire Upon the Deep, 'the coming technological singularity'. The singularity is the moment at which, in Vinge's own words, 'we will have the technological means to create superhuman intelligence'. Shortly after that, again according to Vinge, 'the human era will be ended'. His epic novel clearly reflects his ideas - many of the beings in A Fire Upon the Deep live in a post-singularity universe - but it is also an unabashed and enthralling example of contemporary space opera. It is a book in which unfettered speculation about future technology and a more old-fashioned delight in the creation of alien worlds combine to brilliant effect.