I understand that it is side project that's why I went to Openlibrary website to check results there. And the thing I don't understand is why Openlibrary shows me books that aren't available to borrow. In this case I was expecting that books in search result will be available to borrow. Now after searching for a book you have manually search for a available book. Why don't they put a checkbox 'Show only available books' that would automatically filter out unavailable books?