The Rev. Jesse Jackson yesterday added his voice to the protest against shortened hours at the public reading rooms of the Library of Congress.

"Today we fight for the right to lift our nation by its mind and by its morals," Jackson said on the front steps of the library. ". . . The Gramm-Rudman-Hollings hog-butcher legislation will undercut education in this country."

Jackson made these remarks shortly after 5:30 p.m., the new closing time for the reading rooms. Until March 10 they were open until 9:30 p.m. weekdays, but an $18.3 million budget cut this year caused library officials to close them early on weekdays, except Wednesdays; they are also now closed Sundays. Jackson remained in the main reading room until 5:35, when Associate Librarian of Congress Donald C. Curran mounted the platform in the middle of the large room and shouted that everyone was there illegally.

Curran's voice was all but drowned out by more than 100 protesters singing "The Star-Spangled Banner" and "America."

Then Jackson, holding the hand of 7-year-old Jessica Walls of Haverford, Pa., marched out of the room without being arrested.

Asked by reporters later why he had decided not to be arrested, Jackson said, "We're going to continue to build public attention. We'll come back again."

Nearly 20 protesters have been arrested in the main reading room since March 10, and seven of them have received letters denying them any further access to the library. The "Books, Not Bombs" protests have been organized by Russell Mokhiber, 31, a lawyer with the Corporate Accountability Research Group, a Ralph Nader organization.

Jackson arrived about 5 p.m. on the library's front steps, where a group of schoolchildren from Springfield, Mo., was sitting.

Jackson mentioned yesterday's U.S. military action off the coast of Libya and said, "We must say to this administration to choose books over bombs and give peace and life a chance."

Then Jackson reached out and picked up little Jessica Walls, who had her hair in pigtails tied with bright ribbons. Together, they held up a copy of "Watership Down," an allegorical novel about rabbits.

Then, holding hands and followed by a crush of people, they went inside the main reading room and began looking for a book about the Rev. Martin Luther King Jr.

John Walls, Jessica's father, said he and his wife and two children (Jessica has a 10-year-old brother, Jack) were just in town for a couple of days as tourists. It was a surprise, he said, when Jessica ended up helping Jackson in the protest.

"This is Jessica's first time in Washington. She loves books and I wanted to bring her here and show here this great building," said Walls, who teaches health education at the Haverford School. Jessica is in the second grade at Sacred Heart Academy in Bryn Mawr, Pa.

Inside, she sat beside Jackson as he told reporters, "We are here to fight for access to books because books represent the oxygen for our minds." He added, "Give us libraries, give us books, give us food, give us jobs, or give us death!"

Outside again, someone leaned down and asked Jessica if she knew why she was there. She smiled and didn't seem too sure.

Then someone next to her told her, "Books, not bombs!"