Any s-f survey that begins with an account of Kornbluth and Pohi's matchless Space Merchants can't be all bad. It's not exactly the encyclopedic treatment you may have been waiting for, but it has more than sporadic interest. Once past the usual half-assed survey of The Roots (from the legend of Daedalus to Frankenstein), Ash hits his stride with H.G. Wells. In fact, the book is dominated by the figure of Wells, whom Ash sees as the magisterial formulator of virtually every issue ""discovered"" by later s-f writers. Ash makes an initial effort to discuss the subject in historical sequence, but abandons it after 1930 or so. If he has a thesis, it is that s-f is a uniquely valuable instrument of social criticism and analysis, and as part of this function he treats the main standbys of the genre -- utopias and what Ash calls dystopias, the role of the machine (including computers, robots, androids), time travel, contact with aliens, future moral dilemmas of the human race. Not awfully profound, and not the handiest of introductions for non-initiates, but stimulating. The futuristically minded will observe with pleasure that the copyright information includes a warning about reproduction in ""any information storage and retrieval system now known or to be invented.