Displaying your book on Google Book Search is an excellent way to enable potential customers to browse your book online and buy it.
Also, including your book on Google Book Search, which is free, ensures that Google searches on keywords pertaining to your book display it as part of the search results. Google reports that science books are the most successful in attracting users.
The service enables customers to browse only those portions of your book determined by you. They usually are allowed to see a book's table of contents, index and selected chapter segments that they have found through keyword searches. Printing and image copying functions are disabled on the Google Book Search pages, so readers cannot download or reproduce your content.
Google offers a guide to Google Book Search that details the features of the service and its Partner Program. There are also an information page for publishers and authors and a page specifically for authors that discuss how to participate and offer examples of the service's use in marketing. You might also consider uploading your book to Google Book Search through the new Constellation service, which enables publishers to submit books to multiple digital vendors in one step.
A user browsing your book can buy the book from any outlets that you determine — for example, Amazon.com, Barnes&Noble.com or your own Web site — by clicking on links on the page.
You can also earn revenue by allowing Google to post contextual ads on the site next to your pages. For example, an astronomy book might also have ads for telescopes appearing next to the book's pages.
To enter the program, you need to hold the copyright to your book. You can either send a hard copy of the book or upload it as a pdf file.
The Google Book Search Help Center includes a comprehensive set of answers to questions.
Beyond Google Book Search, there are also a multitude of other ways you can use Google and other social media to promote your books. The techniques described by media consultant Amy Gahran in her article Findability: A key technique for expanding your freelance business also apply to book promotion.