Blast from the past here! Quick feature request - we're working on an ebook and a couple of things seem a little counter-intuitive or buried...
1) Invite new user. This is the first thing I want to do, it seems pretty buried in admin. Might make sense to add this to Home screen under create a book etc (really emphasises the social aspect of the tool!)?
2) Invite user to group. This doesn't exist right? Again, we want to get social, Would be great to have a step after creating a group that allows you to invite new members, either by username, or new users via their email address. Think of the viral potential! :)
Yes, the social aspect of the tool has not fully flourished as it really should :) Yes, invite new user is one of the things which should be more accessible. Invite new users to join you in editing, invite new users to proof-read your book (and only have read permissions), invite some people to read and comment and etc. Many times there is no reason for these people to have accounts in Booktype. For instance random url could be easily created protected with password.
There are many possibilities and some of them are already on the todo list. At the moment we are rewriting editing interface from scratch and changes in front end (with features like you suggested) will come after that.