This is a convenient way to search library resources from anywhere. Some examples:
References in Wikipedia will have “Check for Full Text” added on the page. Click on that to see if the library has the article.
When you perform a Google search (turn Instant Search off for best results), you will get an icon to automatically search the library’s holdings.
Websites where books are reviewed will ususally include the ISBN. The toolbar changes ISBNs into links that will automatically search the library catalog.
Watch for a new version coming in the next months that will work in Chrome and have other great features.