As Claus just announced, we are writing a book with Hadrian on Apache Camel entitled "Camel in Action".
There has been a real need for such a book for a long time. We're hoping to fill the gap in the current documentation thats out there and provide a go to resource for new and experienced users alike.
A neat thing about writing at Manning is that readers can see the book as its being written (in all its rough glory :)) and provide feedback directly to us. Also its early enough in the writing process so that you could have real influence on what topics get included!
Feel free to check out the book and forums.