It was 20 years ago, journalist Liston argues, that the National Security Agency set up the spy ship USS Pueblo as a juicy, poisoned plum to be grabbed by the North Koreans--a ploy by the United States to aid in the breaking of a Soviet code system. Liston, who admits that he is not an expert in this arena, claims to have unveiled a conspiracy that eight other books and a heated Congressional inquiry (his primary sources of information) failed to discover. Although he weaves a troubling tale, Liston's histrionics and innuendoes weaken his credibility. He tantalizes with questions, but tends to leave the discerning reader with more doubts than clear answers.