Turned out to be a much less interesting book than I had hoped. Win Scott, who was CIA Station Chief in Mexico City during the 1960's, was a minor figure. The central chapters deal, in a very convoluted fashion, with Oswald's visit to the Soviet and Cuban Embassies in Mexico City in September 1963, and introduce some new evidence to show that the CIA knew more about these visits than they subsequently let on. But Morley does not add anything of great significance.
One sidelight, Morley is currently involved in a FOIA suit to get the CIA to cough-up information about George Joannides, who was CIA liaison to the 1970's HSCA investigation (see Fonzi) -- though the CIA never mentioned that Joannides was knee-deep in the handling of the Oswald appearance in Mexico City both after AND before the assassination.
As I have said in other reviews, though many think I'm nuts, it is my view that a thorough reading of the literature shows conclusively not only that Kennedy was killed by a conspiracy, organized by the American Right and the CIA and executed by men associated with the Anti-Castro organizations in Miami and New Orleans, but that so much is now known about these events that the old saw "that we'll never know" is simply absurd and willful blindness. It is, in fact, "case closed" -- but in a manner that Gerald Posner would never have wished for.