What's read in the corridors of power

* A collection of essays by 40 authors on the definition of ''public affairs.''

* Separate conference studies on housing, workers' compensation, and the farmer's right to farm.

* A book-length study of urban decline and the decay of American cities.

* Approaches to the civil rights of children in receiving bilingual education.

These are only a few of the hundreds of subjects covered in books available from think-tank presses, which operate as adjuncts of centers for public-policy research. Most are nonprofit operations, their major purpose being to inform and enlighten the reader. Like many lobbyist groups, what they want most of all is the public ear.

One opinion of think tanks is that the work is published by and for a strictly in-crowd clientele, far away from the public eye. Those doing the publishing today, in other words, will be back in the agencies tomorrow, continuing the projects and research that began in a policy forum during some previous administration.

Others take a less cynical view. Ron Copeland, a special assistant to the secretary of housing and urban development during the Carter years, admits that inbreeding does occur, but he feels that some policymakers listen to the experts. ''Many of these,'' he admits, ''are in high-level Cabinet positions. I think their services are often more important to the public than the public knows.''

The 1980s are tough times for commerical publishing houses. Many are folding, merging, or just getting by, and university presses are turning to fiction and poetry. Yet think-tank research seems to be on the rise.

One explanation for this margin of survival is that presses with public-policy imprints are heavily subsidized by their parent centers. These institutions, in turn, receive contributions from foundations and the public. Many are also supported by government grants that total in the millions.

Another explanation is that, now more than ever, people are hungry for facts and figures. We're seeing a kind of crisis management in such areas as the national economy, unemployment, defense, and environmental problems. And readers want their answers stripped free of the philosophical and historical context a university press might emphasize. Authors are usually less interested in having the definitive last word than in offering immediate, nuts-and-bolts alternatives.

This emphasis on the quick remedy, far from being a drawback, is becoming an attractive feature to many think-tank publishers. Pamela Riley, director of public affairs at San Francisco's Institute for Contemporary Studies, suggests that readers today ''have an immense curiosity to explore every aspect of a problem.'' Still, the bewildering number of issues makes it impossible to cover every subject in detail. The institute's current ''Federal Budget: Economics and Politics'' is a case in point. With a sweeping compendium of views, it suggests more approaches than solutions.

While there is little attempt at background and perspective, there is likewise no pretense at belles-lettres, no conscious stabs at artistic form and structure. In a world of no-nonsense charts and graphs, there's hardly room for style. As one critic said recently, after looking through a stack of policy publications, ''All books from think tanks read as though they were written by committee.''

Perhaps the most venerable center for public-policy making is the Brookings Institution, which publishes 20 to 25 books a year. Subjects currently in print range from a study of thrift institutions to a look at the 1983 federal budget. Projects under way deal with the handicapped, abortion, and security in the Middle East.

Brookings's stability comes in part from a strong backlist of titles. Arthur Okun's ''Equality and Efficiency,'' first published in 1975, continues to sell about 10,000 copies a year as required reading in economics courses. Just behind it is ''Systematic Thinking for Social Action'' (1971), Alice Rivlin's combination of sociology and political economy.

Although every think tank carries a popular image of political persuasion, the institutions themselves work hard to escape labels of liberal or conservative, and they bristle at any suggestion of editorial bias. Published works result from the research of individual fellows or associates of the center , most of whom happen to share similar points of view.

The Hoover Institution, a West Coast counterpart to the Brookings, has been identified as the spawning ground for many positions taken by the Reagan administration. The Hoover Press publishes about 25 scholarly works a year and in 1982 has enjoyed a 35 percent sales increase over last year. Its major current title is ''The Tax Revolt,'' an update on Proposition 13 by Alvin Rabushka and Pauline Ryan, senior fellows at the institution.

Like similar presses, the Hoover makes little attempt to market its lists through general bookstore trade. But two years ago its massive volume, ''The United States in the 1980s,'' hit the best-seller lists after being touted as an official handbook of candidate Reagan. A collection of articles by 32 Hoover scholars, more than half of them members of the presidential campaign, this wide-ranging treatment of national issues has brought new hope for expanded markets. Coming up this fall is ''New Force on the Left,'' a study of Tom Hayden and the Campaign for Economic Democracy.

Hoover's success is stimulating hopes at other policy presses. The Cato Institute, which moved this year from San Francisco to Washington, is pushing Peter J. Ferrara's ''Social Security: Averting the Crisis,'' being published this month. Advance reviews are favorable, and the timeliness of the subject is unquestionably a point in its favor. ''The key is the title and topic, not the marketing,'' says Janet Nelson, Cato's director of public affairs.

The specialized subject is often as much as a single press can handle, particularly when the center itself concentrates on a limited number of issues. The Conference on Alternative State and Local Policies turns out a blizzard of magazines, briefs, manuals, and reports on local government touching everything from pension funds to solar energy.

Another single-interest research group is the American Land Forum, a small but active organization in Bethesda, Md. Its most recent effort is ''The American Cropland Crisis,'' showing the vast amount of US farm acreage being lost and what the government is doing about it.

Arms control and defense are perhaps the focus of more policy attention than any other issue. The Reagan administration's defense posture accounts for much of this concentration, along with groundswell movements favoring disarmament. The Center for Defense Information publishes its Monitor 10 times yearly, with essays on defense. The Arms Control Association, which published in July a collection of five essays on the nuclear freeze and arms talks, has worked for 11 years in support of US disarmament initiatives. The Center for Conflict Studies at the University of New Brunswick in Canada published early this summer a collection of views entitled ''No Substitute for Peace.'' Brookings has its own Studies in Defense Policy, a respected series with recent looks at US arms sales to Taiwan and the problems of blacks in the American military. The Council on Economic Priorities has published studies of the MX missile and congressional lobbying by the Pentagon.

The American Enterprise Institute for Public Policy Research, known for its conservative economics, is currently taking a renewed interest in defense questions and their effect on international programs. And since 1961 the Hudson Institute has published more than 90 studies of strategic policy and arms control. With the recent addition of former Secretary of State Alexander Haig to its list of fellows, the Hudson will no doubt continue its concentration on defense and foreign policy.

It's unlikely that think-tank publications will be found in neighborhood bookstores or on the supermarket racks. ''We're definitely not on the impulse-buying shelves,'' one marketer commented. But the dependence of policymakers on their meticulous research has never been more evident than in the Reagan White House. And by the time the November election returns are in, there will surely be another spate of political analysis. Then come projections on the '84 elections.