To help promote the launch of  new books, HarperCollins has launched a new Facebook app called Like to Read. The app lets Facebook users who like a book see an excerpt from that book. Then once the book passes a certain threshold of likes, the publisher releases an additional excerpt from that book, rewarding social networkers for sharing the book with additional content.

The first book the publisher has promoted with the app is Into the Darkest Corner by Elizabeth Haynes. Every time the likes hit 500, the publisher gives away another excerpt. So far, the book has likes garnered more than 7,000 likes.

The idea stemmed from the publisher’s desire to “activate” fans. Publishers’ Weekly has more: “Harper is supplementing the excerpts by hosting a discussion with fans on Facebook. ‘We’re trying to grow a community and continue the conversation,’ said associate marketing director Katie O’Callaghan. ‘We want the fans engaged, and invested. If they’re participating, and sharing their experience with their friends, then the content will always be fresh and relevant.’”

William Morrow has just launched a version of the app for Laura Lippmann’s next book And When She Was Good.