FINALLY, ABOUT A year ago, what David and his father call the "decompression" period was over. For the first time in seven years, Julie Nixon Eisenhower found she was able to walk through Washington unrecognized and undisturbed. "At that moment," she writes in the introduction to "Special People," her book of six profiles, "I realized a new period of my life had begun. David and I were no longer at the center . . ."

It is one of the ironies, admittedly small, that now, on a national tour to promote her book, she is trying to get people to remember her.

"Excuse me," a teen-age girl interrupts her at Boston's Logan Airport "Were you on television today?"

"Yes, I've written a book and I was talking about it," Julie Eisenhower replies.

"I knew it. I just knew it," giggles the girl, delighted with herself for having spotted a familiar face in the crowd. Her companions watch with undisguised admiration. Then she pauses because the mystery is not solved completely. "Who are you?" she asks.

"See," Julie Eisenhower says later. "Nobody recognizes me."

The timing is "so poor," coming as it does on the heels of the David Frost interviews with her father. "Unfortunate," she says, "because they (reporters) can't ask my parents what they thought of the broadcasts so they ask me."

Still, Julie Eisenhower is managing to cope. Fame may be "a kind of death," a favorite Anne Morrow Lindbergh quotation of hers, but it also has some advantages. If her face is no longer magazine-familiar, her name is. And already, even before Simon and Schuster came out this month with a heady first printing of 50,000 copies, her book has been excerpted by two leading women's magazines and chosen as a summer selection by the Literary Guild.

In Boston, which is not exactly Nixon country if the '72 election is still a valid weathervane, she has been booked onto three television shows sandwiched around a couple of newspaper interviews.

Simon and Schuster has attempted to set ground rules outlawing questions about her father, her mother, Watergate or the Frost series - so stories will focus on her book, says Eisenhower, which is the reason she is flacking the first place. "I don't want anyone sending political reporters to interview me."

She finds her reception mixed.

"With all the interviews you have to put up with, what questions irritate you the most?" deferentially begins one talk show co-host. "I don't want to make any mistakes."

Across town, a little later, another follows the editorial decision of the show's producers by deliberately avoiding mention of the Frost interviews or for that matter, "anything political." Afterward, a production aide says she told Eisenhower "than in this area there wasn't any hostility to the (Frost) shows. People thought of them as good TV. She seemed to understand what I meant, because she nodded."

At a midday tapping of a public affairs show the moderator is coolly indignant over Simon and Schuster's efforts to limit subject matter. "We compromised," she explains. "The only ground rules I set for my guest reporters is that I don't want anyone trying to score points off her."

But the press has had little or no access to any Nixon since August, 1974, and these regional reporters want some matters cleared up. So there are some scoring attempts anyway.

"What," one asks, "was your feeling about the criticism from a lot of people that your father was telling the truth for profit?"

"What do you expect me to answer, as the daughter?" asks the daughter.

"I don't know. What would you answer?"

"I would answer," answers Julie Nixon Eisenhower, her brown eyes flashing, "that that's an unfair allegation."

What has become apparent from her media marathon is that Americans have an insatiable curiosity, nay appetite, for intimate glimpses of Richard Nixon and his family. If satisfying it presents a special ordeal for Julie Eisenhower, she conceals it with the composure of the pool she's been most of her life.

Occasionally, there are signs that she is vexed. Then, without an instant's hesitation, she is once again her father's most respected public defender and apologist, the identical dual roles she assumed with such dogged determination in the dark days of Watergate. Then a White House press corps was moved to call her "the only credible Nixon."

Did she, for example, ever feel it necessary to make the choice between her duty as his daughter or as a citizen? comes one question under the kleigs.

"I never felt there was any choice to make," she bristles. "I believe in my father. I believe in what he did for his country. I also believe that in 10 years' time your perspective on this era would be quite different . . . I think it's time to step back and let historians analyze the period."

The relex to protect is automatic because if she could ever spare either of her parents any pain, "I would."

There are, in fact, no new questions, only new ways to pose them. "I've had them all before," she says wearily, back in the limousine cruising between Boston appointments.

More disconcerting even than questions she did expect is one suggesting a chink - that as she appears to be in person, so she is in her writing, "too restrained."

It touches a nerve.

"I just don't see that," she says, looking out the window.

The "whole key," first in conceiving and later in doing the interview for her book, was access. If she hadn't would never have gotten to talk to Golda Meir. Or Ruth Bell Graham. Or Anne Morrow Lindbergh. Or Mamie Dowd Eisenhower. Or entertained Prince Charles. Or been invited to China to meet Mao Tse-tung.

But having readily conceded that and also that "of course, I'm conscious all the time of who my father is - with a double name like Nixon-Eisenhower, everytime I sign a check I'm conscious of it," she then insists that her book must stand on its merits, on its writing.

She is writing, she says, because she is trying to find a way to express herself and to grow as a person. Everyone needs to feel his or her life has meaning - "I need to feel I'm a contributing member of society." She sees herself as particularly well-suited to interviewing others, drawing them out, perhaps, and showing what is behind their public facades. "I've been interviewed so much." Her switch of career fields - there was teaching for a while but it is too structured for her lifestyle now - has nothing to do with being disillusioned by politics."No, I believe in out government system." In fact, she and David might well become community activists at some point. She might even manage a political campaign.

"It's funny," says this 28-year-old, about to become 29, "but I feel I've lived a whole lifetime. You know, people change careers in midlife and I'm at any midlife change of careers."

"You know," says a TV engineer, monitoring that remark from a control room screen, "she is damned good."

Another time, in the car, she says she could be on a lecture tour "right now, only making a great deal of money but probably drawing tremendous crowds by presenting the other side to Watergate, but that's not my role and it's not what my parents want me to do."

So it was "not so much as a President's daughter" writing "Special People" as it was someone looking into these people's lives, searching for the private, unknown, never-seen side of them behind the not necessarily accurate public images.

She knows a thing or two about that."After my father was elected President, it was so difficult to be on (Smith College) campus and be one of the students and singled out as the President's daughter . . . Sometimes I was written about as a symbol of the squares. I didn't want to be a symbol of anybody . . ."

In her book, she writes that "it's more difficult for the person in the public eye to communicate with others. You become cautious and circumspect. It dampens you spirit. It is easy to lose one's perspective."

A Boston television audience hears her speak of Washington and there is a note of disdain as she describes how "you meet a lot of people in government and in embassies who have been there so long that by the time they've been there 10 or 15 years, it's all an act."

She returns briefly to that thought later. Those Washington people "almost begin to believe their own press stories," something she says she never did while living at the White House because "it was something I was conscious of so it wasn't a danger."

There is, of course, the other possibility - reading about yourself for your family and being "uncomfortable" with the interpretation. And there is yet another which is new for her, being the writer and wondering what you subject thinks of what you have written.

She worried so about what Mamie Eisenhower would think fo her profile in "Special People" that she never let Mamie see the unpublished manuscript. "It was cowardly of me." As it turned out, Mamie Eisenhower liked it.

"Let me tell you, having been on both sides," says Julie Eisenhower, "very few people like what's written about them."

When she was preparing to go "public" again, in this tour, "The thought did cross my mind: 'Do I want to give an interview to The Post?' In all candor, if I'm going to be realistic and live in the real world, there's no point in carrying on a grudge."

And later, still.

No, she isn't going to comment on waht her father thinks of the press or its Watergate coverage. She falls silent as the car moves through Boston streets, then breaks it herself. "I bet he goes into it in great depth in his book - if you can wait a few months."

Her dark hair is cut short, framing the round face with its somber brown eyes. "How do you like it?" she asks, touching her yellow jersey dress. "My mother is taking Cortisone for her arthritis and it makes her swell up, so she lets me wear this dress."

The luggage, stowed in the trunk, is also borrowed, the Chinese characters identifying it as Pat Nixon's, still intact from the two trips she and Richard Nixon made to the People's Republic of China.

"I really think her spirit is good . . . she is gardening some . . . exercising in the pool a little," says Eisenhower at various points of her mother's gradual return to better health.

Her mother is "uncannily" like Anne Morrow Lindbergh - or vice versa - and one day Julie Eisenhower plans to write Pat Nixon's biography, an oft-repeated vow. Not an insider's view of Watergate - "I don't think the world needs to know my views on Watergate." Nor a book about her father - "I'm not really sure I want to go into the presidency."

Objectivity may be impossibel for a writer, she says, but the "honest" ones recognise their prejudices, try to overcome their hostilities. She wants advocacy journalism left to the editorial pages or "up front" in the magazines. And "I really don't like mind-reading type journalism."

At the airport, waiting to board the flight to Washington, she appears weary but at the same time more relaxed and unguarded than at any other time this day. She nods her head, agreeing with Richard Nixon's explansition of Pat Nixon's stroke: Two days before she had been striken, she read Woodward and Bernstein's "The Final Days."

"It's fiction," Julie says, her voice rising alightly. "I mean, if you had your marriage analyzed untruly - intimate details - in a book, something as devastating as that."

Leaning forward, she twirls the plastic cup in front of her. Her mother has never discussed the book with her, but "if I were my mother, I would say that since 1946 I've given so much of my life to my nation - really, she's worked so hard - and then to be written off.

"The portrait of her was as a non-functioning person, not even as a support to my father in the last days. And it wasn't that way. She's always been a support."

Julie Eisenhower's publisher has ticketed her first class, but she remembers how, shortly after her father resigned and she was flying out to California, the only seat left was a center one in coach.

"I felt like a spider under a microscope. Everybody knew who I was and was trying to read over my shoulder."

Which is one reason, she laughs, why she probably won't be writing any novels. Everybody would be trying to figure out what she meant.

Mind-reading journalism again.

At Washington's National Airport, there is another limousine. It will take her to the Jefferson Hotel and, the next day, a half-dozen back-to-back interview appointments.

She was born in Washington, actually not far from Columbia Plaza where a she and David lived until they moved to New York a year ago. Now they're living in a rented beach house in California - 15 minutes from her parents.

The limousine has turned now onto East Executive Avenue, past the Treasury Building heading north toward Pennsylvania Avenue. On her left, where she also used to live, is the White House.

She never gives it a passing glance.