Using the Google Books service, you can search and navigate material that previously was available only in print form much in the same way you use Google's search engine to comb the world's web sites. [...] he Google Books API allows you to search the database, interact with the service's social features such as retrieve and submit user reviews, view and manage users' book collections, and even embed the book preview interface into your web site.

He includes a few snippets of code showing how to use the Zend_Gdata component to search for books by things like keyword or ISBN number and to pull the records back and display them in a simple table.