I always liked the plot point in "Tinker Tailor Soldier Spy" that active spies would turn to a retired spy when they needed to fix something wrong in their agency. But Dulles' story feels more plausible: A CIA director created systemic problems. He was forced out after a debacle. But the people in his agency still came to him, asked him for direction. And the CIA kept pulling stunts that blew up in their faces… It's hard to know whether the CIA assassinated President JFK; but it's pretty clear that on Dulles' watch, the CIA gathered many goons so over-enthusiastic about political assassination such that they thought killing JFK would be a good idea.
The book's a slow read. The text flows well, but you have to keep pausing and contemplating how much better off the USA would be if someone mentally competent had been running the CIA during those years.