If one has any doubt about the vacuousness of most diplomatic summits, this book by Gorbachev's interpreter at the 1987 summit with Ronald Reagan in Washington, D.C., should remove it. Not that this is the author's intention. Korchilov, an appealing man who now lives in New York City, was entranced by an Elvis record as a youth, decided to learn English, and rose to the top of a highly demanding profession. It's clear that his presence at the summit left him somewhat dazzled; he regales us with lists of those who attended and with some of the less entrancing conversations. (""Welcome to the United States of America. We are delighted to have you here,"" George Shultz tells Gorbachev.) There is a good deal of that kind of thing, as leaders tell pointless jokes, assure each other of the historic nature of what they are doing, and are photographed walking together and smiling broadly as they talk to each other in languages they don't understand. The greatest interest lies in vignettes, as when Reagan tells Gorbachev how appalled he is by the brutal way in which the KGB treated Russian crowds that pressed in on him and Gorbachev winces but makes no reply; or when Gorbachev recounts how party bosses fought over who was to inherit the Lincoln Continental Brezhnev had been given; or in Korchilov's offhand comment that Gorbachev and his wife behave ""like normal people,"" devoid of the arrogance ""so characteristic of most Soviet leaders of the past."" Korchilov believes that there was a diminution in Gorbachev's energy and sense of direction in his last year in office, but concludes that, while he may have destroyed the Soviet Union by mistake, ""his reform program consciously and deliberately discredited the old Soviet system."" A good deal of this stream has been exhaustively panned, but there are some nuggets here.