It has long been known that the Warren Commission ... was flawed in ways that led to generations of conspiracy theories about what happened on Nov. 22, 1963. A [new] book from former New York Times reporter Philip Shenon digs into exactly what the commission got wrong, both by intentional concealment, or, in Shenon's view, extensive attempts by both the CIA and FBI to withhold just how much they knew about Kennedy assassin Lee Harvey Oswald. Much of the truth about the Kennedy assassination has still not been told, [and] much of the evidence about the president's murder was covered up or destroyed - shredded, incinerated, or erased - before it could reach the commission," Shenon writes in the prologue to A Cruel and Shocking Act: The Secret History of the Kennedy Assassination, which draws its title from the first sentence of the commission's report. Shenon tells the story of how Navy pathologist James Humes threw his blood-stained notes from Kennedy's autopsy into the fire after he transcribed a fresh copy of the report. He said that he wanted to keep the documents from falling into the hands of "ghouls," and gave a similar rationale for ordering that the sheets that covered Kennedy's head wounds in Dallas be laundered during the autopsy. The commission's investigators never even saw the photos and X-rays from the autopsy. Shenon also points to the CIA as having taken great steps to cover up their knowledge of Oswald's visit to Mexico City before the assassination.