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When you search for the ISBN and look at the listing here, if there's a blue and white "order this book" button, then there are copies available, so it's not a wish list book. If there's no blue and white order button, look over to the right site of the listing, underneath the publisher and book type. It will say if there are members wishing, and how many.
Another way is to rate the book (by clicking the stars.) This adds the book to your BIR (books I've read) list. On that list, if it's a wish list book, you'll see a large W. A red W means the first person in line will have 48 hours to accept your offer. A green W means the first wisher has it on auto-request, so when you post it and it's offered to the first wisher, the server will accept the offer for the wisher.