I've run into a problem recently where a few books that are recommended to me aren't available in my country, in this case the US. They just haven't been published through a US publisher, meaning I can't recommend them to the library or get them from a non-Amazon bookstore. I've got one that was published in the UK a while back, but won't be published in the US until next year. It would be nice if there was a way to filter that so I'm not getting recommendations for books I can't actually get my hands on.