This is a FANTASTIC extension! When browsing Amazon books, this just shows up on the page, and tells me if the book is available at in my local public library systems- I can click through to my library, put a hold on it at my nearby branch, and get an e-mail from the library when it's ready to pick up. Voila! And it's FREE- great for books you want to read, but not necessarily buy. This, and bookfinder.com, and you'll be in (real) book heaven.