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A Cozy Book Club, in a Virtual Reading Room
By ANNE EISENBERG

WHEN many people think of online social networking, they picture Web sites where the young and the restless discuss their love lives and their favorite bands. But Kathryn Havemann, 60, of Dayton, Ohio, has joined a different sort of Web-based network — one where people are linked by a more sedate interest: their book collections.

“I would never put my life out on the Internet,” she said, “except through my books.”
Social networks that tap the interests and buying power of traditionally reserved groups like the bookish are a small but growing force on the Web. Ms. Havemann, for example, is among the 150,000 or so members of LibraryThing (www.LibraryThing.com), a site that lets people create detailed online book catalogs, learn about the collections of other members, discover shared favorites and swap recommendations.

Creating a catalog on the Web site is easy. Enter the title of one of your books, and the search engine supplies the rest of the details, like the International Standard Book Number, or ISBN, and a thumbnail image of the cover. Click again, and list the next item.
You can view or print your catalog instantly, sorted by author, for example, or by more personal tags like “books that mention Venice,” “books that touch on digital photography” or “books I’ve loaned out.” Collections can also be displayed by book covers.

Ms. Havemann, for instance, has catalogued all of the 2,956 volumes at her home, and no longer has to rely on hand-written notes or a spreadsheet. Now, as she collects new books — an unending and delightful process — she uses a portable bar-code scanner to accumulate their ISBNs, then downloads up to 500 entries at a time onto LibraryThing.

But the swift, accurate cataloguing of her books is not what she prizes most about LibraryThing.
“I love the social aspect,” she said.

Many social connections thrive at the site. Although members can keep all details of their online catalog private, most choose to display their libraries, so Ms. Havemann can learn about other members’ collections just as she might if she visited their homes.

For example, software on the site shows her who else among the members has the same titles she has. All the information is listed by user name, which does not have to be one’s real name; that means bookworms can remain anonymous while sharing the details of their collections. There are more than 1,500 discussion groups on the site, too, as well as shared information on the tags or descriptive words that members use to keep track of their books.

LibraryThing carries no advertising. It is supported by commissions from Amazon.com for books bought through the site, and by member fees. Registration is simple: just enter a user name and password, click on “Add books,” and begin.

The first 200 books can be catalogued free; after that, the cost is $10 a year or $25 for a lifetime membership. AbeBooks, an online bookseller, owns a 40 percent share in LibraryThing.
Other sites, too, including Shelfari and aNobii, are building online book cataloguing and social networking services.

Tim Spalding, founder and president of LibraryThing, which is based in Portland, Me., says that while the site was founded in 2005, it is still in what he calls “perpetual beta,” as the software is steadily being improved. “We plan on staying in beta,” he said. “It’s a sign of constant innovation.” So far, more than 10 million books have been catalogued there.

Mr. Spalding, who studied Greek and Latin as a graduate student and is now a Web site developer, wrote the software based on his own bibliographic interests. To compile data like publication dates for each catalog entry, the application searches Amazon, the Library of Congress and 70 other libraries that provide open access to their collections.

Based on data gathered at the site, Mr. Spalding has written programs that recommend books that members may want to read, or may want to skip, based on their own interests. For instance, he said, if you liked “The Structure of Scientific Revolutions” by Thomas S. Kuhn, the program suggests that you are not likely to enjoy “The Virgin’s Lover” by Philippa Gregory.
One way that Mr. Spalding generates site statistics is by analyzing the tags or key words that people use to help them categorize and remember their books. For example, people cataloguing a new detective novel by Donna Leon might add tags like “Guido Brunetti” (the sleuth) or “Venice” (the setting).

When new members add a book by Ms. Leon to their catalogs, for example, all of the tags that others have used to classify the book appear automatically in the bibliographic data. Click on a tag, and it will lead to the user name of its creator, and in turn to that person’s other book choices.

In this way, people can explore one another’s book categories, as they might once have wandered the library stacks, hoping for unexpected finds.

TAGGING is also becoming important to the ways that Internet services raise money, said David L. Sifry, founder and chief executive of Technorati, a company in San Francisco that tracks the tags people use to mark items on the Internet — including those at photo- and video-sharing sites.

Mr. Sifry said advertisers of a product like automobiles will pay a premium of $50 to $150 above the base rate to have their names on a page that many readers have tagged with words related to “car.”

Mr. Spalding, too, plans to take advantage of the targeted-audience information created by tagging to generate revenue.

For example, he is in the process of selling some of his recommendations data, which is based in part on tagging statistics, to other sites that sell books and book information.

Ms. Havemann, who works an indexing analyst at LexisNexis, which offers sophisticated search services, uses tags at LibraryThing because they are helpful in jogging her memory of a specific book’s contents.

“One book can run into another,” she said, “but if I tag a book by a character’s name, for instance, I can remember the book later.” She also checks other people’s tags to see if she wants to add any of their books to her library.

“It’s wonderful,” she said, summing up her experience on the LibraryThing site, “to know there are many other crazy people out there who are absolutely addicted to books.”