THIS BOOK IS in a class by itself. One of the extraordinary things about Liv Ullmann's autobiography is how little it depends upon the author's celebrity for its power. Yes, she did write it herself and yes, she writes very well.

Ullmann's reflections belong to the growing body of literature by women about the delicate and complex business of being at once an artist, mother, lover, thinker, creator of magic, and wiper-up of spills. By saying so much in so few words and with so great a respect for the privacy of other people (notably, Ingmar Bergman and their daughter, Linn), Ullmann reminds us that it is possible for writers to explore their own lives in print without betraying the trust of friends and lovers. You don't find out whether any of the men in Ullmann's life suffer from impotence or bad breath. What a relief from the endless volume of confessional impulse run amuck.

As an artist and a woman, Ullmann is most deeply concerned with the process of shedding roles defined by others and becoming what she calls "one's best or truest self." Her perspective as an actress sets this concern in a particularly interesting light. Acting does, after all, involve playing roles; perhaps that is why so many people confuse acting with impersonation or imitation. Ullmann sets this confusion to rights in long passage dealing with her approach to the character of Nora in "A Doll's House" and of Marianne in "Scenes From a Marriage." She shows us that a real actor is one who draws from a deep well of emotion and experience and intellect to present a character - that the unexamined role is not worth filling.

Nor, in Ullmann's view, is the real woman who plays roles thrust upon her by others. "I used to want to lodge in someone's pocket," she writes, "and be able to jump in and out whenever it suited me. Now I go around listening for cries from women who I imagine are locked in others' pockets."

But surely, I can hear men (and a good many women) saying, a woman as talented and beautiful and successful and rich as Liv Ullmann has no need to agonize over questions about "the female role." In her struggle to achieve an equilibrium between her responsibilities to herself and her obligations to others, Ullmann is like most women who have refused to settle for one role in life. Her inner turmoil is tempered by a sense of humor and the realization that she is more privileged than most women simply by virtue of being able to earn a good living, but it is turmoil.

Like other women, Ullmann feels guilty a great deal of the time because of the conflicts between the demands of her profession and the demands of motherhood. While she is working on her book, she doesn't dare play records because she is afraid her daughter and housekeeper will think she is frittering away her time in the solitary pleasure of listening to music.

Ullmann returns to the subject of maternal guilt again and again and the concept is usually translated from the Norwegian as "bad conscience." The idea of guilt as "bad conscience" is imbedded in many Northern European languages and it seems especially appropriate in this context. Ullmann is touring Norway with the cast of "A Doll's House" and she can only talk to her daughter on the telephone. The guilty mother looks forward to returning to Oslo and spending time with Linn once again: "We shall have days of belonging together, but gradually my conscience will start limiting me - the letters unanswered, the things undone. And gradually I will become the professional woman again, and be onstage in front of a camera or at meetings, and think of her there at home, whom I always seem to fall because I can't find any solution throught which her childhood and my life as an adult woman can be combined.

"As people do in books, and as I think other women manage to do in their homes."

This book is not devoted entirely to guilt and love and high art and other serious topics; Ullman laughs both at herself and at the other people involved in the public life of a star. There are slightly zany sections about a mixed-up blind date with Henry Kissinger and lunch with self-important editors who are considering her for the cover of Time.

Changing is filled with compassion for the ways in which both men and women have been limited by traditional views of masculinity and femininity. Ullmann dissects "A Doll's House" at great length and it is clear that she regards both Nora and Helmer as prisoners of sex. Her view of relations between the sexes belongs to a feminist ethos that insists the liberation of women will also free men; it is totally at variance with the wing of the feminist movement that suggests women cannot be free until they are free of men.

"If only we all could accept that there is no difference between us where human values are concerned. Whatever sex. Whatever the life we have chosen to live.

"I have my periods and my menopause; and my horror of sagging breasts, and my awareness of the young girl who is me and whom you can no longer see in my face.

"And he has his prestige and difficulties in his job and fear of going bald and becoming impotent and his doubts; and the insecurity he has from when he was thirteen.

"We are together with out problems.We are not dangerous or threatening to each other - not in the moment we feel that we need each other."

It is an idealistic belief arrived at by a woman who has worked hard to take the responsibility for her own life.