A Deepness in the Sky (Zones of Thought series Book 2)

A Deepness in the Sky is a science fiction novel by American writer Vernor Vinge. Published in 1999, the novel is a loose prequel (set twenty thousand years earlier) to his earlier novel A Fire Upon the Deep (1992). The title is coined by one of the story's main characters in a debate, in a reference to the hibernating habits of his species and to the vastness of space.