***** SPOILER ALERT *****

How do you make the perfect slave? A slave who loves to serve you? But more than that, who is like Rainman, an autistic savant, totally focused on some problem you give them, to the point of forgetting to dress themselves, eat, drink, or any other necessary bodily functions while doing things with their minds that shouldn't be possible? They not only work but think themselves to death for you. Meet Focus, the genetic technology developed by the Emergents to make themselves the ultimate slavemasters. Shades of House Harkonnen to the nth power. This is the main feature of the fine novel by Vernor Vinge. But there is more. Imagine a sun that goes on every so many years, then goes off for far longer: an OnOff star. What kind of life would evolve on one of its planets? Vinge answers this: a race of sapient knee-high spiders, every bit as sapient as humans. They spend the cold years in deepnesses, but one prophet sees a future in space, hence the title. Add these elements to the story line in Vinge's earlier work A Fire Upon the Deep, and you get the epic prince warlord hero Pham Nuwen into the bargain. Pham, betrayed by his own, lives incognito while plotting and planning a comeback. Meanwhile, he's found himself on a Qen Ho expedition to the OnOff Star, where they meet an expedition of Emergents (human like themselves), whereupon the sparks fly as they vie for the up-and-coming spider world's resources in quite different ways. A tad long, and with an ending that many will consider as deus ex machina, it satisfies the need for readable, capable hard science fiction, and is another brick in a grand space opera series no doubt. 4 out of 5 stars.