The people who write books are having a spat with the people who print and bind them, and there's a lot more than literary ego riding on the outcome.

At issue is a 1891 federal law requiring most books written by Americans and published by U.S. companies to be manufactured in this country. The law is scheduled to expire July 1.

Book manufacturers and labor unions, fearful of competition from low-cost foreign printing plants, want Congress to extend it. The Authors League of America, which represents such prominent writers as John Hersey, Elizabeth Janeway and Barbara Tuchman, wants to let the law die, as do the publishers and several departments of the Reagan administration.

The administration has told Congress it wants to give the Office of the U.S. Trade Representative the power to negotiate book-import provisions with individual foreign countries, rather than to maintain a blanket prohibition. For that reason, the administration has declined to endorse a Labor Department study that says expiration of the law "could cause a direct long-run loss of 78,000 to 172,000 employment opportunities in the printing and publishing industry."

That study has provided heavy ammunition for the book manufacturers and the unions, who fear the competition of printing plants in Singapore, Japan and Hong Kong. But it has been denounced by other participants in the dispute as exaggerated and misleading, and the administration has declined to permit the author of the study, Michael Moore, to testify at House Judiciary subcommittee hearings.

The law, which is part of the copyright code, provides that nondramatic, literary material written in English by Americans who live in the United States must be printed and bound in the United States or Canada. The law covers most of the books, catalogues, textbooks, business reports and newspapers produced by the nation's $68-billion-a-year printing and publishing industry.

Congress decided in 1976 that there was "no justification in principle" for the rule and set its expiration for July 1, 1982. With that date approaching, the participants are lobbying furiously with the House Judiciary subcommittee on courts and civil liberties, which is considering an extension.

Last week authors league President Harrison E. Salisbury sent a telegram to subcommittee Chairman Robert W. Kastenmeier (D-Wis.) saying that, if the rule is extended, it should be made applicable to books by foreign authors as well. Otherwise, Salisbury said, "U.S. authors will be severely handicapped in their competition with foreign authors" for inclusion in publishers' lists.

At the same time, lobbyists for the Book Manufacturers Institute distributed a new paper by Moore, author of the Labor Department study, defending its findings and suggesting that they actually understate the potential job loss.

A "fact sheet" by the Book Manufacturers' Washington lawyer, Stephen F. Owen Jr., cites a consultant's study estimating that "between 30 and 45 percent of the books now manufactured in the U.S. could, in a five- to seven-year period, be produced overseas," mostly in the Far East. The fact sheet was accompanied by an article from a Singapore newspaper headed "Good Times Ahead for Local Printers" as the U.S. law expires.

Carol Risher, a Washington representative of the Association of American Publishers, said "we strongly advocate expiration. The law still limits to some extent the opportunity for an American author to be published abroad, and we think it's unconstitutional--it discriminates between one class of book authors, Americans, and all others in the rest of the world."

She said repeal would not lead to mass foreign printing. "Publishers need certainty, we need quality control, we need to be able to print in a hurry when some school committee suddenly approves a textbook and orders 20,000 copies," she said.

The probable outcome is a short-term extension of the law that will not resolve the underlying issue but will allow time for further study by Congress and the administration, according to sources in Congress. Kastenmeier introduced a bill last week that would extend the rule as it now stands for three years, without applying it to foreign authors.