The mods said it's for security reasons that has something to do with copyright issues of a book being shared. Though I didn't get the gist of it, that's what the rule is right now. 20 or more post and you are allowed in the reading room.
The rules have been changed and users are now required to participate more so the forum can be better. You can get to 20 points by sharing and commenting on posts, etc. For example, this post I am writing right now will gain me 1 extra point.
So, surf the forum and try to help other users by your posts!!