Now that I have Library Extension, I'm not sure I can function without it. It works great and saves me tons of dough on books.
I'd love to see Carnegie Library and state university library catalogs among those available in the extension, but Idk if those are available publicly in the way that the currently included library catalogs are, so it may not be possible (yet) to include them. Other than that tiny nitpick, this is a fantastic extension and I highly recommend it.

I love it. and don't worry publishers & authors (except Macmillan imprints, which I'm boycotting bc of the company's library policy): I often still buy the book even when my library has a copy - before, I would often put of deciding to buy until I checked library holdings, and then I'd forget to come back to purchase. This way I have that data immediately.

Works perfectly, a great extension!

This a wonderful and useful extension! Will save you a lot of money if you are a bookworm like me.

One of the most useful extensions ever! Simple, accurate - and I use it on 3 libraries in my city.

Great extension, works as advertised. Very helpful to see library availability while browsing for books.

Library Extension is great. Performs as advertised... easily and quickly exposing if a book is available in my local library (Philadelphia Free Library... yeah!).

Incredibly useful with my local library, and also with Overdrive. Helps me avoid the tax-avoiding monopoly that is Amazon.

I used to do the library lookup separately. This app has saved me many hours of searching my library database to see if the books are there. And it also allows me to go directly to my library and put the book on hold. Amazing!

Great way to see if a book is in my library's collection. Love how easy it is to use.

Found out about this extension from a Book RIot article. Works flawlessly for me and my library system.