The seven National Book Award winners were announced yesterday afternoon without fanfare, but the National Book Award week ahead promises to have its usual full share of festivities, in-fighting and controversy.

Wallace Stegner took the fiction prize with his novel "The Spectator Bird," about a retired literary agent living out his last years in California - recalling his existence as a "fellow traveler in the lives of other people and a tourist in his own." (Stegner won the Pulitzer Prize in 1972 for "Angle of Repose.")

"Norman Thomas: The Last Idealist," by W.A. Swanberg, won in the category of biography and autobiography, and Irving Howe's "World of Our Fathers" won in the history category.

There used to be awards for an "Arts and Letters" and a "Contemporary Affairs" category, but those have now been combined under the heading of "Contemporary Thoughts." The winner of that prize is "The Uses of Enchantment: The Meaning and Importance of Fairy Tales," by Bruno Bettelheim.

The award for best children's book went to Katharine Paterson of Takoma Park, Md., for her tale of 18th-century Japan. "The Master Puppeteer."

Richard-Eberhart won the National Book Award for poetry this year for "Collected Poems: 1930-1976," while the prize for translation (the only category in which judges considered books published in 1975 as well as 1976) went to "Master Tung's Western Chamber Romance: A Chinese Chantefable," translated by Ch'en Li-li.

There have been rumors of dissension between publicity conscious publishers, who sponsor the awards, and the staid National Academy and Institute of Arts and Letters, which has administered them for the last two years.

And there has been open controversy surrounding the prizes themselves, at least since the nominations were announced in March.

Several winners of the National Book Critics Circle Awards, for instance, were not even nominated for the NBA, including John Gardner's novel "October Light", "the Woman Warrior" by Mazine Hong Kingston, and Elizabeth Bishop's book of poems,, "Geography III."

"Roots," the publishing phenomenon of the year and possibly the decade, was not nominated in any category, though it was considered in fiction, biography and "Contemporary Thoughts" before the history judges were asked to make a final decision. They have awarded it a special citation for its "distinguished literary quality."

The regular awards, which include a cash prize of $1,000, will be presented to the winners Wednesday night at the auditorium of the American Academy and Institute of Arts and Letters in New York.