an online resource that lets you search the collections of thousands of libraries across the world

Do I need to use WorldCat?

You can use WorldCat to search for your book; the results will show you which libraries have your book in their collection. You might like seeing the results, but be aware that not all libraries are connected to WorldCat, which means you won’t get the whole picture from this website alone. There are more copies of your book in libraries than WorldCat reports.

Link to WorldCat.