Believe it or not, I am only now getting around to reading James Douglass's book JFK and the Unspeakable: Why He Died and Why It Matters. I am nearly done with it. On balance, I am every impressed with it. The book does a great job of bringing together the evidence that Oswald was an intelligence operative and that elements of the U.S. intelligence community, especially elements of the CIA, were involved in the plot to kill JFK. But the book spends far too much time preaching far-left political views. The book could have been 30 pages shorter if most of the political preaching had been removed.
The leftist tilt of so many pro-conspiracy books reinforces the perception that you cannot be a conservative and believe that JFK was killed by a conspiracy, that rejecting the Warren Commission's version of the shooting means you are liberal, anti-military, anti-U.S. intelligence, and even unpatriotic and prone to paranoia.
I think it is unfortunate that so many pro-conspiracy books condemn the U.S. attempt to preserve South Vietnam's independence, i.e., the Vietnam War. Why do so many pro-conspiracy authors contend that our effort to enable South Vietnam to become another South Korea was evil and imperialistic? The Korean War had its ugly and tragic aspects, and plenty of civilian casualties, but look at the result, especially compared to North Korea. Would anyone seriously suggest that the Korean Peninsula would have been better off if we had not intervened to preserve South Korea's independence? The South Vietnamese government, for all of its faults, was far better than North Vietnam's brutal communist regime.
It certainly does not help matters that some JFK conspiracy theorists have defended the nutty, irrational conspiracy theory that 9/11 was an inside job, that the Twin Towers and a nearby building were destroyed by controlled demolitions, that the Pentagon was not hit by a airliner but by a missile, etc. I live in Northern Virginia. I know people who saw the airliner flying barely 200 feet above the ground and heading straight for the Pentagon. One of my co-workers was working as a security guard at the Pentagon on 9/11 and saw part of the plane's fuselage inside the building (he still suffers from a lung condition caused by the smoke he inhaled that day).
I think the most effective pro-conspiracy books are the ones that stick to the facts of the case and that do not attempt to use the case as a springboard for pushing this the author's political views, whatever they might be.