RICHARD NIXON'S fifth book since resigning the presidency addresses one of the central failures of his administration, the war in Vietnam. The result is interesting as a treatise in self- justification, but as a work of history it is a bust.

Nixon won the office in 1968 in large measure on the promise that he would gain "peace with honor" in the conflict which had come to dominate American public life. Many Americans were skeptical that he could accomplish this feat -- Nixon was refusing to say how he would do it -- but the majority was willing to let him try.

Through prodigious efforts at political and military maneuver and a cost of 15,000 more American combat deaths plus even heavier Vietnamese casualties on his watch, Nixon was able to drag out the war for four years. He finally brought the GIs and POWs home under the terms of the Paris accords of January 1973, which left communist forces in a strong position inside South Vietnam.

The South Vietnamese government of President Nguyen Van Thieu bitterly protested that the deal was a disguised "surrender," but Nixon forced Saigon's acceptance of the best terms he could get. Two years later, Hanoi attacked again in full force and Saigon collapsed.

Nixon's argument in this book is that with his program of Vietnamization plus episodic heavy bombing and ground attacks on communist supply lines, "we won the war." Moreover, "We signed the peace agreement that ended the war in a way that won the peace. We had redeemed our pledge to keep South Vietnam free."

Unhappily this isn't the ending that we all remember. On the page after declaring victory, Nixon explains that his hard-won triumph in Paris and Indochina "was thrown away in a spasm of congressional irresponsibility. . . . Congress proceeded to snatch defeat from the jaws of victory" by forbidding new U.S. military action and reducing U.S. aid to the Saigon government.

In order to make this case, Nixon ignores or plays down several important factors: the unyielding determination of the Vietnamese communists to continue the war at all costs, the fragility and fear of the South Vietnamese regime and, above all, the declining support for the war in Congress and the U.S. public as seemingly endless struggle wore on. Nixon never acknowledges that his sudden episodes of bombing, incursion and bravado, which are presented here as military or political necessities, intensified the opposition to the war and encouraged the imposition of congressionally-imposed limits by raising grave questions about his intentions.

Nixon has reconsidered the Vietnam battleground before, in his more extensive 1978 memoirs. A considerable part of the new account of his stewardship of the war -- which is the most important part of this book -- is taken word for word from the earlier work. On the other hand, the differences between the two accounts are fascinating. Some of them suggest a doctoring of history, at least his version of it, to make his conduct and his case appear better this time around.

In the current volume, for example, Nixon claims that by November 1972, U.S. bombing had "succeeded in crippling North Vietnam's military effort." He also claims that due to its failure on the ground in South Vietnam earlier in the year, "Hanoi's armed forces were in tatters" and that "Vietnamization had worked. Our ally had stopped the spring offensive on the ground, and our bombing had crushed it."

These claims were not made in Nixon's earlier memoirs RN. There he quotes from his personal diary during the 1972 offensive: "The real problem is that the enemy is willing to sacrifice in order to win, while the South Vietnamese simply aren't willing to pay that much of a price in order to avoid losing." In the memoirs Nixon reports that Thieu broke into tears in October 1972, on learning from Henry Kissinger that a Washington-Hanoi deal might not require the withdrawal of North Vietnamese troops from the south. "I sympathized with Thieu's position. Almost the entire North Vietnamese Army -- an estimated 120,000 troops that had poured across the DMZ during the spring invasion -- were still in South Vietnam," the earlier book reported. I

N NO MORE VIETNAMS his treatment of Thieu and the crucial withdrawal issue in the Paris accords is

misleading, deceptive, yes, tricky. Nixon concedes that he agreed not to require North Vietnam to withdraw its forces from the south because, "If we had stood firm in demanding North Vietnam's withdrawal, there would have been no peace agreement." He insists that the Paris arrangement "tacitly required the enemy to withdraw" because "we demanded that Hanoi pledge to stop the infiltration of men into South Vietnam" and thus "if the promise was kept, enemy forces in the south soon would have to withdraw or else wither away."

The Paris agreement contained no such North Vietnamese pledge. The document required the South Vietnamese communists not to accept new troops or advisers, but permitted them to replace "armaments, munitions and war material" on a piece-for- piece basis after the ceasefire.

As for Thieu, Nixon through most of the present volume speaks of the South Vietnamese leader's "wholehearted" support for U.S. plans and "close cooperation." He does not disclose -- as he did in his memoirs -- that Thieu objected from the beginning to the plan to "Vietnamize" the war through the gradual withdrawal of U.S. forces.

Nixon treats Thieu's opposition to the Paris agreements as distressing but puzzling. Thieu "seemed oblivious to to the crucial issue. South Vietnam's survival did not depend on whether enemy troops occupied a few sparsely populated regions. It depended on whether the United States enforced the terms of the peace agreement, both with continuing aid and with a credible threat of military action," writes Nixon in the current volume.

The "crucial issue," as Nixon describes it, was precisely what was worrying Thieu, with good reason. In his memoirs -- but not here -- Nixon quotes a diary entry of October, 1972: "What really concerns (Thieu), Henry (Kissinger) believes, and I am inclined to think he is right, is that he is terrified of the idea of the Americans being gone from South Vietnam." When the G.I.s did go home, U.S. support indeed collapsed.

In the current volume Nixon writes that Thieu persisted in refusing to sign the accords despite "enormous pressure" from Washington until Nixon made it clear the U.S. would go ahead without him. "I sympathized with Thieu and shared his concerns," Nixon writes. Kissinger in his memoirs quoted Nixon as saying at the time, "Brutality is nothing. You have never seen it if this son-of-a-bitch doesn't go along, believe me."

No matter how you tell it, the story of how Congress forced an end to U.S. involvement following the Paris accords and the withdrawal of American troops is an inglorious, shabby episode. Nixon tells it with relish, blaming the lawmakers for refusing to let him redeem his secret pledge to Thieu to respond swiftly and militarily if the communists persisted despite the Paris agreement.

Nixon writes here, as elsewhere, as if the president's power to wage war as he wishes is beyond question or challenge from Congress or anyone else. This may have been the case before the Vietnam war but is no longer so, in part because of Nixon's imperial attitude. The rest of the American political system revolted against the unbridled application of military power in an unpopular war. The War Powers Resolution and other restrictions imposed then have changed the American system and affected the U.S. role in the world.

In addition to Nixon's account of his own decisions about Vietnam, he covers key decisions of his predecessors. He seems tougher on them and less impressed by the limitations under which they had to work than by those imposed on him.

The first and final chapters of No More Vietnams provide the book with an overlay of Nixonian geopolitics, expressed in the broad strokes which Nixon finds more congenial (and which this reader also finds easier to accept) than the detailed account of his own involvement.

No More Vietnams seems clearly timed to take commercial advantage of the 10th anniversary of the fall of Saigon, which is being commemorated as the new Nixon book is published. Actually the book is a bit late. In the tradition of George Orwell and "Doublethink" it should have been published in 1984.