With the arrival of  "Facebook messenger unseen" on IOS and Chrome, users can now read their Facebook messages without it been marked as seen, thereby not notifying the sender that their messages has been read by the recipient.
Facebook messenger unseen app which works on IOS devices such as iphone, ipod touch and ipad running on ios 6.1 and above will at first use ask for permission to access your Facebook data, when it is granted access it synchronizes all your Facebook messages and enables you to read all messages within the application and  keeps the message unread in your Facebook messenger.
  It can be downloaded for free from Cydia at the MOdMyl Repo on IOS devices and also on chrome store as plugins on Google chrome.

http://www.etechvillablog.com/2013/09/how-to-stay-unseen-on-facebook-messenger.html/

facebook could be a very complex social network. I found some interesting articles and post to get through facebook. below are some of their most important links.