“Society never advances. It recedes as fast on one side as it gains on the other.... For every thing that is given, something is taken,” wrote Ralph Waldo Emerson in his 1841 essay “Self-Reliance.”

The newest application of this old wisdom involves the world of book buying. Amazon.com, the Web’s best e-commerce site, is also the world’s largest bookseller, and it has recently introduced new features that make book buying even more enjoyable, convenient, and economical. But these same features have some book authors reaching for their poison pens.

Amazon.com for some time has done a great job of providing context about a book to help you make a buying decision. Unlike in a bookstore, you can quickly search for books by title, author, and subject, and with any books that look interesting, you can read reviews by professional book reviewers and fellow readers. With many books, you can also browse through a limited number of pages to see if the author’s writing style fits your expectations.

With some books, you can now also “Search Inside the Book.” You type in a search term, and Amazon.com finds books containing the term and lets you access any page containing it plus the two preceding and the two following pages. This is what has caused the controversy.

The Authors Guild, an advocacy group for writers, tested Amazon.com’s “Search Inside the Book” feature and discovered you could copy and print out more than 100 consecutive pages from a single book, though doing so was time-consuming. Amazon.com has since disabled the print capability, but you can still, without much technical expertise, capture the screen and print it out otherwise.

What would stop you ... besides your conscience ... from collecting cooking recipes or travel suggestions this way, without having to buy the book? “Most reference books [are] at clear risk in such a database,” said the Authors Guild in an e-mail message to members. For this reason, not all book publishers participate in the program.

Amazon.com defends “Search Inside the Book” by pointing to its utility. “We believe that the more information you give a customer about the products they’re interested in buying, the more of those products they actually buy,” said Jani Baker, director of product public relations, in a phone interview. In the first 5days of the “Search Inside the Book” program, sales of books that were included in the program were 9 percent higher than sales of non-participating books, she said.

In various online discussion groups, readers are overwhelmingly positive about the feature, as expected. Fiction writers also like it—readers need the entire novel. Nonfiction writers are divided, with some supporting it. Karen Heyman, a science writer in Santa Monica, Calif., feels it will be a boon to researchers while not hurting authors.

If fully implemented, she said in an e-mail interview, “it will spare you having to spend hours in a library going through the indexes of dozens of books on the off chance one of them might have something applicable.” She doesn’t see it reducing book sales. “I completely agree with the idea that this will lead to more books sales, not less, because you get introduced to many books you wouldn’t otherwise have found.”

The ultimate would be for Amazon.com to become a Google for all published content. Just as you can search the Web now, in the future you may be able to search through the typically higher-quality information published in books. Time will tell if this will happen comprehensively and how it will affect book sales.

Fewer sales is also a concern with another Amazon.com feature, “Marketplace,” where you can buy used books from fellow readers as easily as you can buy new books from publishers. The savings can be dramatic, and the potential loss of earnings to book authors is self-evident.

Amazon.com defends this practice as well. “Amazon.com is all about selling more books and helping customers find and buy books they wouldn’t have known about,” said Baker.

“We’ve found by offering customers lower priced options, it causes them to visit the site more frequently, which in turns leads to higher sales of new books,” she continued. “It encourages people to try authors and genres that they might not otherwise have tried. Also, when customers sell used books, they have more `budget' to buy new books.”

What is clear is that it’s a changing world out there, in book publishing and the larger world of information technology. As always with change, there are winners and losers.