The "Check Library" bookmarklet lets you know whether a title is available at your library from bookstores and other websites across the web. It checks all the editions of the title, not just the edition you're looking at.
How do I get it?
To get the "Check Library" bookmarklet, just drag the big blue button to your browser's "bookmarks" bar.
How do I use it?
To use it, go to a book webpage and click the bookmarklet that is now in your browser's bookmarks bar.