WorldCat

I must confess, this is a tool that I have been using almost daily during my trainee rotation in ACT. I searched for a book (Into the Wild), and OCL came up as the closest library holding the title. About the only difference regarding location results is that when you are logged in as part of ILL, OCL is displayed in green text to make sure you realize that we hold the book, and not to search elsewhere for it.

WorldCat will definitely help you and your customer complete a Request for Materials form. About the only information that I found missing was the publication month and the price. Following the link to Amazon can get you the month of publication, but Amazon did not have a "realistic" price for the edition that I was looking at; only prices which varied by quite a bit from resellers.

WorldCat will work for filling out the form. Whatever info is missing from WorldCat, can probably be supplemented from Amazon.