If you read about a book in The New York Times, chances are Cornell University Library has it on its shelves -- or will in a few days. If you found a citation to an article in the Journal of Really Important Stuff, chances are the library has it, or at least can get a copy of the article.

Cornell's library, one of the 10 largest academic research libraries in the United States, holds almost 8 million print volumes in 18 libraries on the Ithaca campus and in those at the Weill Cornell Medical College in New York City and Geneva Agricultural Experiment Station, and adds more than 125,000 more each year, along with an increasing number of digital books and an array of "nonbooks" -- maps, motion pictures, slides and filmstrips, sound recordings, videotapes, DVDs and microforms.

The library subscribes to 60,578 print serials -- mostly scholarly journals -- and an ever-growing number of online databases, and provides access to more than 47,000 full-text electronic journals; 6,068 electronic journals were added last year, some replacing the paper versions.

Who decides what to buy? Librarians, of course, consulting with faculty and students.

John Saylor, interim associate university librarian for scholarly communications and collections, has overall responsibility for collection development. Some buying decisions, which Saylor calls "macro," are based on the assumption that the library needs all the material published by a specific scholarly society, university press or respected publisher. For example, the library automatically buys every scholarly publication from the Association for Computing Machinery, nearly every computer how-to book published by O'Reilly, most scholarly publications from nearly every university press in North America, the science fiction/fantasy output from Tor Books and books from respected small-press literary publishers such as Copper Canyon Press and Alice James Books.

About 30,000 volumes a year are bought through approval plans, where vendors automatically send certain materials, and the library sends back anything it doesn't want -- usually only a small percentage. The library also receives advance announcement of what books will appear in The New York Times Book Review, and automatically rush orders them. Often the books are on the shelves before reviews appear.

"Micro" buying decisions are made by some 40 "selectors" in the 20 libraries across the university who have specific expertise in areas such as music, chemistry, literature, history or life sciences, working with their own faculty and students and with individual budgets. The library also receives many books as gifts from alumni and other donors. Some generous alumni and faculty have created endowments to support library purchases, often selecting a particular subject area. For example, the Salisbury Fund in Mann Library allows the library to collect extensively in early childhood development. The Hussain Shaukatullah Thermal Sciences Collection Endowment in the Engineering Library enables the continuation of a world-class collection in combustion and heat transfer science and engineering.

The library makes many purchases through consortia, which function as buying clubs. When 10 libraries at once order the same item, they can negotiate a lower price. "Last year we paid $3,500 to belong to the Northeast Regional Libraries consortium," Saylor reports, "and we saved about $75,000."

Of a $16 million annual budget, about $4 million buys new print books; most of the remainder pays for scholarly journals and other online resources.

With more journals -- and even some new books -- coming out in digital form, accounting gets complicated. In the past, you bought a book and you owned it. Now you may buy a license to use the intellectual property, renewed every year. "That costs more, and it costs more to manage it," Saylor says.

In the distant past librarians might put a piece of tape on a journal volume and if it remained unbroken, they would know no one had used the publication. Online journals now supply a more precise count. The Journal of Biomechanics, for example, costs $3,000 a year but was accessed 1,600 times, a reasonable cost per use of $1.94. However, Saylor found another journal costing $6,000 a year that was used only 28 times, at $212 per use. "We'll talk to the faculty and see if we really need that," he says.