There's an extension built for Chrome and coming soon to Firefox that every book blogger should know about.
It's called Library Extension.
What it does is add a little box when you're browsing book pages on Amazon or Goodreads and tells you whether or not your local library (whatever library you use) or has a copy of that book.
Then you can click on through straight to the library's book page.
On Amazon the box appears above the'add to cart' box.
On Goodreads it appears under the book description.
I've been using it for a couple of weeks now and it's really awesome. It saves time to manually look up the book on your library's page and it will no doubt save the moolah and shelf space.
It only works with a limited number of countries, but you have to select yours to make it work anyway. I live in the arse end of nowhere and it even works with my library.
Seriously people, get it now. It's totally awesome.