We've been spending a bunch of time updating our documentation for Community Server lately. The content is great, but the UI is a little iffy still — we're planning on doing an update to the UI in the coming weeks.
In addition to our own documentation we've been working closely with Wrox and Packt on two Community Server books due out in the next several months. The book from Packt will be focused more on using Community Server while Wrox's book is more about developing with Community Server.
The only one listed on Amazon right now is Wrox's book: Professional Community Server written by Wyatt Preul. While neither author worked for Telligent when they began these projects, we did just hire Wyatt. Wyatt is starting off as tester on Scott's team and will be helping get more unit testing into our automated build process. He is also going to work on a new "black-ops" project that we're hoping to roll out later this year.