Shedley has one of the most original imaginations among today's fledgling sf writers; at this stage he hasn't quite figured out what to do with it. His basic idea here is a prolonged vendetta of alien races against humanity, which unwittingly obliterated an inhabited solar system while trying out an interstellar drive. Over the next few eons, mankind--long gone from what was once Earth--tries various strategies to escape the planet-incinerating attacks of the aliens: pretechnological camouflage, relocation to vast shipboard communities, energy-reflecting weapons. And along the way to mankind's final triumph, Shedley hatches wonderful notions--computer-programming through song; an 80-pound Siamese cat bred for wildlife management; a ship's communication program which converses in irreverent pidgin English. These inspirations practically fall over each other, but Shedley never finds the right proportions for his major episodes; they ought to add up to a story, but mostly they just drift around like chunks of matter in free fall. Uneven, then, but alluring.