The publishing industry continues to put out more books than the public is prepared to buy, according to a report issued Monday by the Book Industry Study Group.

The number of books sold dropped by nearly 44 million between 2003 and 2004, even as the annual number of books published approaches 175,000.

"People are reading less, so what you're seeing is the same phenomenon that has hit magazines and newspapers, a massive shift toward home video, DVD, internet and cable," said Albert N. Greco, an industry consultant and a professor of business at the graduate school of Fordham University.

The Book Industry Study Group (search), a nonprofit research organization, reported estimated sales of 2.295 billion books in 2004, compared to an estimated 2.339 billion the previous year. Higher prices enabled net revenues to increase 2.8 percent, to $28.6 billion, but also drove many readers, especially students, to buy used books, Greco said.

The BISG anticipates a better year in 2005, thanks to the new Harry Potter (search) book, "Harry Potter and the Half-Blood Prince," and to a surge in high school and elementary textbook sales, with many states due to order new editions.

"We see that as a temporary spike," Greco said.

After 2005, the BISG expects a flat market for the following four years. Religious titles are an exception, with both dollar sales and the number of actual books sold expected to average more than 6 percent annual growth into 2009.

"The key isn't so much Bibles and prayer books, it's what we call `other' religious books," says Greco, citing such multimillion sellers as Rick Warren's "The Purpose Driven Life" and the "Left Behind" novels of Tim LaHaye and Jerry B. Jenkins.

An especially troubled area, Greco says, is college textbooks. While no hard statistics have been compiled, many believe that students are increasingly turned off by prices for new books and instead buying used editions. The BISG anticipates a steady drop in sales for new works, from 68 million in 2004 to 64.4 million in 2009.

"It's an unbelievably sophisticated business," Greco said of the used textbook market. "You get people visiting campuses and sending students e-mails, encouraging them to sell their books once they're done with them. You have instructors selling their exam copies of textbooks so that students have used editions within a very short time after a new book comes out.

"Another problem is online piracy from abroad, kids downloading texts from Web sites in Asia and other places. I had one student come in and show me the book he was using for my class. It looked exactly like the textbook I assigned, except the illustrations were in black and white."