If you find someone with interesting books in his library, you can add him to a list of favorite libraries. Unfortunately, Google doesn’t show when there are new books in your favorite libraries and doesn’t make it easy to discover libraries that might interest you. Based on the books from your library, Google could recommend other similar books and a list of users with similar tastes. To make the library more personal, people should be able to annotate books and highlight interesting excerpts.
Google, Book Search, Google Profiles, New Features