Jip and Zab are sitting on a rock in Cornwall, playing with their portable computer. A message flashes back on the screen: GET OFF MY BACK. What they're sitting on looks like a stone, but functions like a mega computer with rigorous but occasionally tricky logic, for instance, using both exclusive or (XOR) and non-exclusive OR. They christen it Xorandor.

Jip and Zab are twins. Their father runs a nuclear waste dump and Xorandor feeds off alpha-particles from fissile materials. When he produces offspring programmed with exactly the same functions, the experts see them as a solution to the nuclear waste problem. But things go disastrously wrong.

The narrative is entirely in dialogue since the twins dictate their story into their word-processor, learning as they go the problems of story-telling, memory, and re-handling lived experience, using transcripts, and print-outs when they can. These narrative problems are complicated by their relation to Xorandor himself, pure brain with almost infinite memories, but capable also of syntax-errors when he has absorbed the wrong food.

This hardback book is in great condition and weighs 13 oz.