It's going to be hard times for hardcover books. By 1985, consumers will find booksellers carrying much smaller inventories, stocking a higher percentage of paperback originals and devising creative schemes to fight rising prices.

These are among the findings of a study released yesterday by the Book Industry Study Group, a nonprofit organization representing publishers, wholesalers, manufacturers, libraries and booksellers.

The last major survey of book distribution was conducted in 1931. It showed, according to The New York Herald Tribune, that publishing "has never quite decided whether it's a business or a noble experiment," and that it is "perhaps the most irrational of all our leading economic enterprises." "Fifty years later, we're reading the same thing today," BISG chairman DeWitt C. Baker told a press conference at the Library of Congress' Madison Building. "We're still a fragmented industry."

The report surveyed some 200 industry experts about problems in the book distribution process and prospects for change. Some likely trends:

* As production costs of hardcovers rise, books that originate in paperback, with no hardcover editions, will increase from approximately 20 percent of the market now to between 30 and 40 percent by 1985, and as high as 60 percent by 1990.

* Although the overall number of new books (some 40,000 new trade titles were released last year) is not expected to decline, book suppliers will cut back significantly on inventory. They will order smaller quantities more frequently, necessitating increased use of telecommunications, faster reporting of retail sales figures and greater cooperation among segments of the industry.

* As booksellers are forced to pay more in shipping costs to return unsold volumes, "self-remaindering"--in which the stores themselves discount overstocked books--will become attractive. Like record-sellers, booksellers will try to find ways to "get rid of them at the retail level," said Neil Doppelt of Arthur Andersen & Co., the accounting firm that conducted the survey for BISG. At present, large returns are sold to remainder specialists, whose role is expected to grow considerably by 1990.

* Retail prices may begin to reflect the cost of transportation. "As it is now," said Baker, "a book that is printed and sold for $10 on the East Coast is then shipped to the West Coast and sold at the same price." Publishers' suggested retail prices may be altered accordingly.

* "Electronic delivery" of books to video screens will not have a significant impact until 1990, although primary and secondary education programs have begun to use such systems. But if the Reagan administration calls for major cutbacks in education, said BISG secretary Hendrik Edelman, university librarian at Rutgers, "and the bottom line is that there are no dollars at all, then to talk about future trends is moot."

Of all segments of the industry, the burden of change will fall heaviest on traditional trade publishers, according to the survey; but in the short term there will be only "relatively incremental improvements."