THERE WERE SOME people in the office of the Watergate special prosecutor who used to say - mostly, but not entirely in jest - that the thing that finally did in Richard Nixon wasn't the tapes, but the fact that White House guards once kept Leon Jaworski standing outside the gate for nearly a half hour in a snow storm, waiting for clearence. Until that point, they say he had been skeptical about the evidence in the case, sympathetic to the great pressures of the presidency, and not entirely comfortable with the aggressiveness of the staff he had inherited from Archibald Cox. But some of this changed that day in the cold and the snow.

"By the time he got back to the office," says one staffer, "Nixon was guilty." Jaworski would never admit that such a slight affected his judgement, of course. But he was upset enough about it that he takes pains to mention it in his book, and even now, five years after the fact, the annoyance clearly shows through. Angry at the treatment, he telephoned Alexander Haig, then the number-two man in the White House who tried to calm Jaworski by telling him that his own brother, a Jesuit priest, had suffered a similar delay. "Al," Jaworski replied, "I find small comfort in that."

There are several other such insights into Jaworski's mind-set during this period, and they make Confession and Avoidance an interesting, but by no means indispensable, book. We learn, for example, that he came to the conclusion that it would been "unthinkable" to have allowed Nixon to remain in office, but also that it would have been impossible for him to have received a fair trial. We learn that Jaworski came to Washington believing Nixon was innocent, but after listening to the tapes, became convinced that Nixon was "a paranoid and vindictive man," and guilty as well. And we also learn that Jaworski's own view is that Nixon himself was responsible for the 18 1/2-minute gap in one of the key Watergate tapes.

As news items go, this isn't much. After all, a lot of others came to that same conclusion a long time ago, even without the benefit of the army of technicians Jaworski hired to analyze what was left to the tape. But the purpose of Confession and Avoidance, despite the publisher's hype, doesn't seem to be to make news. Jaworski's intention seems to be to off-set what he sees as creeping revisionism about Watergate, and to build a dike against the flood of revisionism that he expects to come. Most of this is jammed into one angry chapter, called "The Ex-President," which follows nine chapters of anecdotes about lawyering in Texas that only a grandchild could find truly interesting, and precedes one in which he says the handling of the Korean-payola investigation wasn't as bad as most reporters seem to think.

There are Nixon loyalists out there, Jaworski says, "who would not believe him guilty if he had been caught holding a flashlight for the Cubans." This is to be expected, and doesn't appear to concern him. But he obviously is troubled by some others, who lately have been talking about Nixon being a national resource who should be reclaimed.

"The Nixon revisionist literature, including his own, appeared faster than many expected," he says. "Shrewdly, his re-emergence from San Clemente, from his self-imposed 'house arrest,' has been designed the only way it could be. Slowly, infrequently, distantly. On television. In print. At a funeral. In the armory of a small, isolated, partisan town. In foreign lands. Nixon is like a closet plant, able to grow in the shadows but unable to tolerate direct sunlight."

He was not unfairly hounded from office, Jaworski insists. "Anyone who still clings to the notion that Nixon was undone by his enemies can turn to nearly any page [of the transcripts of the White House tapes], any conversation, to see the plotting and conniving and abuse of power that made Watergate a scandal unique in American history."

There are strong words and lively reading, but not representative of the book as a whole. For the greater part, the prose style is of the "Take a letter, Miss Adams" variety. Most of the stories are the sort that lawyers (and reporters) tell each other in bars after work, on out-of-town assignments, and which invariably sound flatter and duller when set into type.

But there also are that help explain just who Jaworski is, and where he came from, and the sort of pressures he had worked under before. Not many lawyers, after all, have had to face the fact that their work helped send 36 men (German war criminals) to be hanged. And not many have undertaken so unpopular a case as the prosecution for civil rights violations of Mississippi governor Ross Barnett (once described by journalist Robert Sherrill as the dumbest politican ever produced by that state, but a hero nonetheless to many in the South).

There are times when one wishes that public heroes would do their duty and then, like Cincinnatus, go back to their farms. But even special prosecutors can be forgiven for wanting to have the last word, and Jaworski can't be faulted for wanting to say more strongly than he has in the past that the evidence justified his having helped chase Nixon out of the White House.

The title of the book comes from a legal term which means, in essence, that the defendant committed the act but - for legal or moral reasons - should be excused. And it also, perhaps unwittingly, is as good a summary as any of the book itself: it has many weaknesses and flaws, but there's just enough merit in it that Jaworski and his co-author should be excused. CAPTION: Drawing, Jacket drawing of Jaworski by Dave Christensen; Picture, Photo of Leon Jaworski by James Atherton - The Washington Post