As stated in their Bookperk email you may purchase a paperback or ebook for $4.99 using code "bookclub". Ten titles to choose from all currently $7.00 - $11.49 at Amazon. While not a fabulous offer it may be a start of further publisher exclusive offers.
WARNING: Their website says only available with the HC app. I don't know if the user agent work around still functions.
http://www.harpercollins.com/weeklyd...9&utm_content=