In re the KGB "Investigation:" The Lee Harvey Oswald sojourn in the USSR has never been documented thoroughly by them. Hell, we still don't even know if the LHO who went into the USSR is the same guy who came out! They sent a false defector over to claim the KGB had "no interest" in him: a patent lie.
As far as JFK ordering the hit on Diem: "Duh," it's been known for years. Ditto, the JFK-Mafia plan to hit Castro.
If we divide up us conspiracy theorists into teams, we have the "Castro-KGB Connection Team," "The Mafia Team," "The CIA Team," "The Johnson Did It Team." I feel badly because my team, "The Castro-KGB Connection Team" never really gets an adequate hearing and it somehow always felt the most "logical" to me.
I promise to read the book and keep an open mind. That's because one learns something new every day. E.G. The Secret CIA Army in Tibet. If JFK let them wither on the vine, it will add evidence to my overriding theory: that the stolen election of 1960 was a watershed event in the history of the United States, namely the final, hopefully-not-irreversible-but-don't bet-on-it, crooked triumph of hosshite over American logic and common sense. Ted Kennedy's Immigration Reform Act of 1965 certainly fits nicely into this pattern of the Kennedy-driven destruction of the nation.