Mr. Vinge writes what might be called thoughtful space opera. His setting is nothing less than the galaxy we call the Milky Way. I don't mean that he simply lets loose a few spaceships and has them chase one another among the stars to act out another old-fashioned shoot-'em-up plot. The human and nonhuman characters of "A Fire Upon the Deep" live in a complex galactic society that Mr. Vinge has worked out in admirable if economical detail, and the scope of his story is such that it requires just a background.