Ferguson’s access to the diaries Kissinger kept before, during and after his visits to Vietnam in 1965 and 1966 allows him to argue, totally convincingly, that on his missions for the Johnson administration, Kissinger realized very early on that the United States had little or no hope of winning the war and therefore needed to enter into direct negotiations with Hanoi sooner rather than later, albeit from a position of strength. This book contains the first full account of the abortive initiative to start talks with Hanoi in 1967; as Ferguson puts it, “to an extent never previously recognized by scholars,” Kissinger attempted “to broker some kind of peace agreement with the North Vietnamese, using a variety of indirect channels of communication to Hanoi that passed through not only Paris but also Moscow.”

Yet it is in Ferguson’s comprehensive demolition of the revisionist accounts of the 1968 election by Seymour Hersh, Christopher Hitchens and others that this book will be seen as controversial. For he totally rejects the conspiracy theory that blames Kissinger for leaking details of the Paris peace negotiations to the Nixon camp, details that enabled Nixon, it was said, to persuade the South Vietnamese that they would get better treatment if he and not Hubert Humphrey were in the White House. Ferguson goes into this theory in great detail, disproving it on several grounds, but especially for its lack of even the most basic actual or circumstantial evidence. (It turns out that one of the reasons Kissinger was in Paris in 1967 was that he was secretly going to the Sorbonne to woo the only great love of his life, Nancy Maginnes, whom he subsequently married.)

Of course it will be in the second volume that Ferguson will come to grips with the revisionists’ attacks on Kissinger’s actions involving places like Chile, Argentina, Cyprus, East Timor and Bangladesh. The book’s introduction strongly implies that he will be acquitting Kissinger of the monstrous charge of war criminality that the revisionists have made over the years.

Yet this is no hagiography. As well as being highly critical of Kissinger’s theory of limited nuclear war, Ferguson describes a letter of his as a “solipsistic screed”; says of one of Kissinger’s books that it “remained, at root, the work of a committee”; and states that Kissinger was “even more demanding to his own subordinates” than Rockefeller was to him: “He learned to rant and rage.” The criticisms — and there are many more waspish ones — absolve Ferguson from the charge of whitewashing Kissinger and make his praise all the more credible.

This is an admiring portrait rather than a particularly affectionate one. Ferguson acknowledges in his preface all of the “conversing with him, supping with him, even traveling with him” that he did over the many years he spent researching and writing this book. But if Kissinger’s official biographer cannot be accused of falling for his subject’s justifiably famed charm, he certainly gives the reader enough evidence to conclude that Henry Kissinger is one of the greatest Americans in the history of the Republic, someone who has been repulsively traduced over several decades and who deserved to have a defense of this comprehensiveness published years ago.

Part of Kissinger’s charm of course derives from his highly developed sense of humor, which is given full rein here. “Nobody will ever win the battle of the ­sexes,” he once joked. “There’s just too much fraternizing with the enemy.” When someone came up to him at a reception and said, “Dr. Kissinger, I want to thank you for saving the world,” he replied, “You’re welcome.” All of this was delivered in the trademark voice that the journalist Oriana Fallaci described as like “that obsessive, hammering sound of rain falling on a roof.”

Niall Ferguson already has many important, scholarly and controversial books to his credit. But if the second volume of “Kissinger” is anywhere near as comprehensive, well written and riveting as the first, this will be his masterpiece.