Microsoft launched its book search in beta form on Wednesday. However, unlike Google's project, publishers must opt-in to have their books included.

Windows Live Search Books would initially be accessed via a separate category on Live Search. But next year, Microsoft plans to integrate the service into its main search product once it exits beta. According to the company, the goal is to link all the various search products into a single interface.

Users of the Search Books product would be able to search the full text inside of the book. Currently, the service only includes books without copyright from the University of California, the University of Toronto, and the British Library.

Partnerships have been announced with two others, the New York Public Library, and the American Museum of Veterinary Medicine. Books still under copyright, however, are not expected until a future release, Microsoft says.

"There is a lot of trusted and authoritative content that can only be found in books today," Microsoft's Publisher Evangelism director Cliff Guren wrote in a Web log post Tuesday. "With this beta launch we've taken our first steps toward making that content discoverable and easy to read."

Microsoft's policies on including content could be fingered as the reason why the service could be seen as getting off to a slow start. Whereas Google has partnered with libraries and scanned books into their search regardless of copyright, Microsoft is asking publishers to opt-in first.

Google's opt-out policy has also gotten it into legal hot water - it is currently fighting two lawsuits in the United States over that policy from both the Author's Guild and the Association of American Publishers.

In related news, Microsoft also announced that it had updated its Academic Search product to include "millions" of new articles, primarily in the bio-medical field. With the addition of the new content, the size of the database has quadrupled, according to the company.

"These are just a few of the most recent examples of our efforts to deliver the most relevant content available; whether it is in a book, in an academic journal or on the web," Guren said.