I just got my copies of the new Professional Community Server book from Wrox!
This book is geared towards the developer and covers topics such as themes, APIs, reports, modifying source code, modules, and much more! Definitely on the recommended reading list if you work with Community Server!
There are several more books planned that will hopefully be started in the next several months. Nevertheless, it's definitely very exciting to see this book come out on a product we've worked so hard on.
P.S., Community Server 2007 will be available on April 15th 2007.