SAN FRANCISCO (AP) - Online search engine leader Google Inc. is becoming more bookish.Expanding a program introduced last year, Google Inc. is inviting publishers to include entire books in its search engine index, enabling people to peek at the content before making a decision on whether to buy the title.

Although the entire books will be scanned into the index, the new feature introduced Wednesday won’t allow people to read the entire books online unless publishers unlock all the content.

Participating publishers must allow people to read at least 20 percent of the books through Google’s search engine, said Susan Wojcicki, Google director of product development.