Radio UserLand Kick Start, a book I'm promoting relentlessly because it needs some help getting onto bookstore shelves: Dave Winer:
David Wall, Amazon.Com:
If you've been wondering about the programming and content management environment behind the blogging tool and aggregator; the object database, verb set, outliner, debugger, website framework, get this book, it's great. I'm really excited about this.
The user-level coverage is comprehensive and patient enough to get you through the moments of confusion that are sure to strike as you learn about the Radio environment. The programming coverage is similarly complete, explaining both theory (like how RSS feeds work) and practice (there are lots of code listings that illustrate popular effects). This book covers its subject fully.