IMO, the Mob was involved using LHO as the patsy and the shooter. I don't believe there were shots fired by anyone else (ie the grassy knoll). I do believe that Oswald slipped out of the book depository to avoid getting caught. I believe Ruby killed him to shut him up, on behalf of the mob.
I do not believe it goes beyond the mob. I don't think the CIA, Lyndon Johnson, Israel, Cuba, the Russians or anyone else was involved. For me, it is pretty simple = the Kennedy's double crossed the mob, and the mob did what they do to people who do that.
I also believe the mob was involved. I also believe LHO was the shooter, or perhaps one of the shooters. But I don't beleive the mob could have done this on their own. They would have needed the support from powerful people within the government to organize the cover up. What I think is that the mob was designated to carry out the assassination, while other parties, such as listed above, were responsible for the cover up.
