I've been writing a book on ESB and SOA for a while now as part of Thomas Erl's SOA series. The publishers have finally put up a page for the book. From my own perspective the content of the book is influenced heavily by what you will find in the JBoss SOA Platform and its roadmap. Of course it's not a technology specific book because it needs to be able to stand on its own, so it is no replacement for the SOA-P documentation. However, you should be able to read it and think "Ah, now that makes sense from a standards perspective", or "OK, so I'd be better of using this pattern here".
When the book is finally released we'll make sure to mention it here. In the meantime you can always go out and get another good book on enterprise SOA.