''This has become a very hot issue since last year, when it just seemed to explode all of a sudden,'' said Ms. Nakoneczny, of the college store association. The association's letter to the publishers warned that the pricing structure might be an antitrust violation. ''The sale of identical books to foreign buyers at prices significantly lower than to domestic buyers, while publicly stating that domestic prices are due to high costs, could constitute an unfair or deceptive act,'' the letter said. While there is no longer protection in the federal copyright law for the pricing differentials, the major publishers are still trying to stop the reimporting of texts priced for foreign markets, mostly through contract language forbidding foreign wholesalers to sell to American distributors. Some have placed stickers on covers, saying ''International Edition RESTRICTED Not for Sale in North America'' or added the cover line ''International Student Edition.''

None of the three major textbook publishers -- Pearson, McGraw Hill, and Thomson -- would discuss why overseas prices are so much lower than domestic ones, referring all questions to Allen Adler, the lawyer for the American Association of Publishers.

''This is a season when textbook publishers get kicked around a lot, and they're feeling vulnerable,'' Mr. Adler said. ''The practice of selling U.S. products abroad at prices keyed to the local market is longstanding. It's not unusual, it doesn't violate public policy and it's certainly not illegal. But publishers are still coming to terms with the dramatic change in the law.''

Mr. Adler contends that foreign textbook prices are pegged to the per capita income and economic conditions of the destination countries -- and that foreign sales are a boon to America's standing in the world, to foreign students seeking an American-quality education, and even to American consumers, since each extra copy sold overseas, even at a low price, helps to spread the high costs of putting out a new textbook.

As more and more customers turn to reimporting books, it is an open question how long the overseas price differentials will last.

''We buy from the U.K., France, Israel and the Far East,'' said Bob Crabb of the University of Minnesota Bookstores. ''As long as the publishers are offering books at less than half the price that's available here, we'll take advantage of it. It's great for students. For publishers, the marginal costs of printing a few extra books and selling them overseas are very, very low. But I would guess that shortly, the sales here will begin eating into their U.S. sales in a serious way.''

Disgruntlement over textbook costs has been growing in the United States as prices have risen. Last month, Senator Charles E. Schumer, Democrat of New York, announced that the average New York college freshman and sophomore spends more than $900 a year on texts -- 41 percent more than in 1998 -- and proposed a plan to make $1,000 of textbook costs tax deductible. The same week, University of Wisconsin students demonstrated against high textbook prices and in favor of creating a textbook rental system.