Library Extension is a browser extension available for Chrome (Firefox coming soon). As you browse websites for books and e-books, the Library Extension can check both the library's online catalog and OverDrive, and displays the availability of that item on the same page.
My initial problem using the extension was an expectation that I needed to click something. I kept clicking the browser extension button on the chrome, only to see information about the extension and not about the book I was viewing in the browser. I was making it too hard: keep looking in the website where you are viewing information about the book, and you will see a box titled "Library Extension" added to the page. In Amazon, it loaded on the right side; in Goodreads, it loaded within the main column.
Availability information is generally correct in my experience so far, but it has failed to find an ebook that we have in our collection. It may also not catch that we have different editions, or it may find a similar book instead of an exact match. It's not perfect, but it can be a time-saver.