Osnos was a reporter during the Vietnam War, later a major publisher in foreign policy, and specifically the publisher of McNamara's mea culpa In Retrospect. The book opens with the promise of revealing previously hidden insights into the two key Americans involved in escalating the Vietnam War, and like a "special extended edition" of a movie, the major take-away is that there's a good reason those scenes weren't included in the first bit.

The book briefly and ably covers the major points of Halberstam's The Best and the Brightest thesis, that a deeply-rooted anticommunism and unexamined assumption of American superiority lead to the major commitment of ground forces and all the bloodshed of the war.

What is beneficial is a little bit of a deeper insight into McNamara's character. I've been fascinating by McNamara since I saw The Fog of War, and how McNamara illuminates the question of how an intelligent and decent man could become enmeshed in atrocity. In McNamara's case, the key issue was one of integrity, which meant loyalty to the dead JFK, with whom he shared a real personal bond, and loyalty to the idea that in the executive branch only the President and Vice-President are elected, and the role of every other member is to support those who have been democratically selected.  You may advise, but once policy has been chosen, the only option is to back the policy.

Both McNamara and Johnson were skeptical of the war relatively early on, in 1963 and 1964. But 1964 was an election year, and Johnson was concerned mostly with not giving Barry Goldwater an avenue to attack him. So a decision on what to do in South Vietnam was pushed off as the situation deteriorated. Johnson was a political operator to the spine, and charting a path between the doves and hawks meant a gradual escalation that satisfied no one and lead to almost the worst of all interventions. Both McNamara and LBJ did their best, but they were unable to find a strategy that could lead to American victory, or a way to sell giving up to the American people.

If there is one word to describe McNamara, it would be 'deliberate', and he definitely planned his series of books and statements in In Retrospect, Argument Without End, and The Fog of War with care. If you're looking for some kind of admission that isn't in those sources, you won't find it here.