The move will allow Microsoft to focus on other types of Internet searches, such as travel listings, Senior Vice President Satya Nadella said in a blog posting Friday. Spokesman Scott Trepanier declined to say how much Redmond, Wash.-based Microsoft had spent on the book project.
"We recognize that this decision comes as disappointing news to our partners," Nadella said.
Microsoft is making changes to its Internet business as it chooses battles with Google, owner of the dominant search engine. Microsoft said this week that it would offer rebates to shoppers who buy products through its Live.com search system, taking a different tack from Google's.
The company started making digital copies of out-of-print books in December 2006, later making deals with publishers to scan their books, after Google started a similar program with libraries. The Microsoft program digitized 750,000 books and indexed 80 million journal articles, Nadella said.
The book-search site didn't get enough users to justify Microsoft's investment, said Clifford Guren, the company's senior director of publisher evangelism for the project. Major publishers are digitizing their own books, he said.
"We had to ask if it was right for us to do this or the publishers," Guren said. "For the publishers, it is in their long-term best interest."
Microsoft owns the third-most-popular U.S. search engine, trailing Google and Yahoo Inc., according to research firm ComScore Inc.
Google's book-search project, which began in 2004, works with Harvard University, the New York Public Library and other organizations to scan books. The company also works with about 10,000 publishers to digitize their books.
Google is "absolutely" continuing the project, spokeswoman Jennie Johnson said in an e-mail.
Though Google hasn't detailed how it will turn book searches into a profitable business, it could use the feature to run ads alongside query results or to share profits with publishers when users buy books or portions of books, said Jim Milliot, news editor at Publishers Weekly, a trade magazine.