When professor Michael Zeller assigns problem sets for his “General Physics” class, he often has to cross-check the two editions of the course’s textbook that students use to ensure that the same questions appear in each.

“The publisher makes them just enough different to drive me crazy,” he said.

Zeller’s headache in formulating assignments results from a national trend of rising textbook prices that prompt many students to borrow books from a friend, order them directly from the publisher at reduced rates or, in the case of Zeller’s students, buy older editions from former students who no longer need theirs. Prices of textbooks have been rising at a rate double that of inflation for two decades, a 2005 study by the Government Accountability Office found.

With final course schedules in and students getting started on the semester’s work, many Yalies said they have become creative in finding ways to get around what are often daunting price tags on their classes’ reading lists.

“I think some of the textbook prices are ridiculous, especially when the professors make you buy a super-expensive book just because they wrote it,” Deanna Arrieta ’09 said. “One of my books cost over $100, and it’s not even a hardcover book. It was difficult to come up with that for just one book.”

Economics professor Ray Fair said one reason he thinks textbook prices have gone up so much in recent years may be the evolution of a stronger used-book market, which means that publishers feel the need to charge higher prices for the smaller number of books they do sell.

“What’s making things so expensive? Is it prices of paper and ink? One thinks not,” Fair said. “The process of printing ought to become more efficient with things becoming more computerized. It’s not clear that you can look at the cost side and explain it. The only idea I have is that it’s this even more efficient used-book market.”

Students in several of Fair’s classes have found the cost of their textbooks prohibitive, Fair said, and have asked his permission to purchase older, cheaper versions of his books. He said he agreed to these requests and others from students who wanted to order the course’s materials from abroad, where books are often cheaper.

“As an economist, you say, ‘Buy it at the cheapest place,'” he said. “If the [Yale] Bookstore is not the cheapest place, then use the Internet.”

School of Management professor Judith Chevalier, who contributed materials to the recent Connecticut Summit on Textbook Costs, said that mergers in the publishing industry may be responsible for the recent surge in book costs.

“Some markets where there were four or five or six competitors now have two or three,” she said.

In order to avoid having to buy the complete syllabi for all her classes, Arrieta said she has resorted to checking books out of the library and has turned to her friends and freshman counselors to ask them for their used books.

Darryl Auguste ’09 said he has found the retail prices for some of his books at the Yale Bookstore to be unreasonable and has looked online for better deals. He sometimes buys books at the Yale Bookstore to use during the first few weeks of class and then returns them for a refund once his shipment arrives, he said.

“I think I’ve probably bought like one book from the Yale Bookstore,” Auguste said. “I buy everything else from Amazon or the publisher. The Yale Bookstore is good if you need a book immediately and then want to return it later.”

Zeller said he is aware of the burden textbook prices place on students and that he takes cost into consideration when choosing books for his classes. But he said that there is little professors can do to reduce prices.

“We simply get told the price of the book,” Zeller said. “And I do try to give a little weight to the price of it. I do let the book salesmen who see me all the time know this is a pretty expensive book and I’m going to look around to see if I can try to find a less expensive book. All I can do is try to put pressure on them that way. That’s the only thing professors have.”

Students in Chevalier’s SOM class, “Competitive Strategy,” often order their textbooks from India for around $8, she said, a price much lower than the $97.40 that Amazon.com charges. Chevalier said students find the reduced price to be more than enough to make up for the fact that the Indian version comes in paperback form, appears on lower-quality paper and is printed in one color instead of three.

Labyrinth Books, which carries textbooks for some Yale classes, receives numerous criticisms from customers that the textbooks it carries are over-priced, owner Cliff Simms said. But those objections should be aimed at publishers, not booksellers, he said.

“It’s always the case that we’re on the front lines of hearing complaints,” Simms said. “But I think they’re misdirected. It’s not the bookstores that are profiting. Publishers have raised prices based on whatever they see as market forces.”

Simms said Labyrinth already prices textbooks at a reduced price that makes selling them minimally profitable. The margin of profits on textbooks is usually between 20 and 30 percent, compared with a 40 percent margin on general-trade books, he said.

Yale Bookstore manager Joe Bender said that, according to company policy, he is not allowed to comment on matters related to pricing. Officials at the national Barnes & Noble office did not return calls for this article.

Yale Student Financial Services offers some students assistance in paying for their books, but the amount of money they allocate for this purpose is often not sufficient, Matthew Traldi ’06 said. Traldi, who is on financial aid, said Student Financial Services has determined that he does not qualify for a book stipend.

“There’s some people for whom the books are put into their financial aid package, but I don’t think it’s ever as high as the bill is for most people most semesters,” he said. “The financial aid office should have a more realistic guess for how much books are going to cost, because right now it’s very low.”

But Director of Financial Aid Caesar Storlazzi said a stipend of $2,700 for books and miscellaneous expenses is included in the budget of every student on financial aid each year. If those expenses exceed the $2,700, the student can contact the financial aid office to seek additional funding, he said.

“We had done a budget survey some years back, and the amount spent on books varies greatly from student to student, and from major to major,” Storlazzi said. “Our books and miscellaneous expense budget item represents an informed average amount.”

Traldi said he buys course packets assigned for his classes but often goes to Cross Campus Library to borrow books on close-reserve for his group IV classes, for which the books tend to be more expensive.

Still, some students said they are willing to pay full price at the Yale Bookstore and Labyrinth because getting books there is more convenient and more reliable than purchasing them online or directly from the publisher.

“Even though I do pay more at the Yale Bookstore, it’s definitely worth it because it saves me so much time and it’s so much more convenient,” Kara Harton ’08 said. “The only time I [buy online] is when I cannot locate a book locally. A lot of times Labyrinth will either run out of a book for a very popular class or professors place orders late and the books don’t come in on time, and then maybe I’ll try to find it elsewhere and order it.”

Harton said that when she tried to order a used textbook on YaleStation last year, the book arrived without a supplementary CD that was supposed to be included, an event that reinforced her preference for buying her books new.

“The CD wasn’t absolutely necessary, but since it came with the book, I would have liked to have it,” she said. “If I had gotten the book at the Yale Bookstore, it would have cost an extra $40, but I would have had that CD.”