UPDATE: This app saves me so much money! PLUS I emailed the app creator about a query, and he answered and solved it - totally worth it. Worth the small donation that was only a very small portion of the money I've saved using the app.
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This is an amazing app - it works on both Amazon and Audible - it's perfect for when I'm curious about an ebook or audiobook, but don't know if I want to buy it to keep, or if it will go in the 'read once and forget' pile. Definitely a money saver! In all, a useful, unobtrusive app. It's a keeper :)

Practically flawless, and in the rare instances a bug is found, the response is helpful and thorough. Been using this extension for years. Absolutely fabulous

I'm a big reader, and this has saved me SO much money! It also helps encourage my local library to get more e-books! Love it!

So good! I don't have to check all my local libraries at once to see if they have it, and I don't have to leave the website I'm on to look it up elsewhere. I use it all the time, and I work at two libraries!

I learned about this through an article - Truly a game changer and something I've been seeking. I find a book that I like, go to my library website to see if they have any copies, if not, consider purchasing which makes me go to another site. This extension automatically allows you to preview how many copies your library has of a book you're reading a review of. Truly - AMAZING. It's worth the caps. Such a time saver. Thank you!!!!

Love this extension, it's saved me so much money and I use my library more

The Library Extension is an indispensible tool and one of my use-every-day apps. Library extension quickly sources book titles from your local library or one of the online repository archives.

Love this app! Saves me so much time and $$!

This is an unobtrusive, well-designed, thoroughly useful add-on. Oh, and it does real good in the world: saves you money, directs more attention to the world's beautiful public libraries, and puts one small roadblock in the way of Amazon world domination.

Automagically and without my asking seamlessly showed that a book I am looking at on Amazon is available in my library. Saved my having to go through a few extra steps to get there.

So glad to have this app as it saves me from buying books that are available in my library or on Scrbd rather than Amazon

Man this little app has changed my life & saved me so much time (especially since NYPL makes you log in EVERY time to do a search). Thank you!!

Edit:

2022-
Still an amazing team. Replies in a flash to any queries or issues you have

2021 - Amazing Team, responds to any issues you have and updates the app in the next few days. Wonderful app that really helps you find the books you have available in your selections.

very helpful as are the people who answer questions for this addin