The Book Bar reminds me of the Recommended Product Links of Amazon Associates. Using that, you can also show books (and other products) that match specific keywords or categories. Unlike the Google Book Bar, Amazon's widget pays you for sales generated through the widget.
The News Bar reminds me of the Topix.net News Widgets (category and zip only) or the keyword search and other widgets of Findory Inline.
Looking at this, what I think would be really cool would be if Google's Book Bar and News Bar self-optimized based on usage of the widget, much like Google AdSense does.
I could imagine two ways of doing that. One would be to adapt to usage of the widget on a particular site. For example, if I put Google Book Bar on my site, the books picked might depend on what books people click on in the Google Book Bar on my site as well as using aggregate information across all sites.
Another would be to personalize the selection of books or news articles to interests of each viewer based on their individual history. For example, the items in your Google search history could influence the news items you see if you view the widget on some weblog. The news personalization in Google Sidebar (part of Google Desktop Search) already does something much like this, featuring news articles based on your past behavior. Amazon Omakase is a good example of a books widget that makes recommendations based on your past behavior, in this case based on your purchase and clickstream history at Amazon.com.