Thread:Unok/@comment-4556650-20140509150805/@comment-3544775-20140801101239

http://www.animate-onlineshop.jp/pn/%E3%80%90%E3%81%9D%E3%81%AE%E4%BB%96%28%E6%9B%B8%E7%B1%8D%29%E3%80%91%E3%80%8C%E4%B8%83%E3%81%A4%E3%81%AE%E5%A4%A7%E7%BD%AA%E3%80%8D%E3%81%AE%E7%A7%98%E5%AF%86/pd/1282052/

http://www.animate-onlineshop.jp/pn/%E3%80%90%E3%81%9D%E3%81%AE%E4%BB%96%28%E6%9B%B8%E7%B1%8D%29%E3%80%91%E4%B8%83%E3%81%A4%E3%81%AE%E5%A4%A7%E7%BD%AA+%E8%A3%8F%E5%88%87%E3%82%8A%E3%81%AE%E6%89%8B%E9%85%8D%E6%9B%B8/pd/1282024/

Not sure if the 2nd one is related to this series, but I suppose it is. Also no idea what those "secret" books are. I saw Toriko having the same thing long time ago. They don't seems to be from the author, so I doubt there will be something that we don't know. I may get the first book and see what's about.