I already own the book, but I wanted to let others know that it is the Manning 'Deal of the Day' today (12/05/10.) You can get it for $25 if you enter promotional code dotd1205ccb when you checkout.
Also, the somewhat-related RabbitMQ in Action is half off today, with code n3050. (After reading the first chapter, it puts zeromq in perspective, if you search HN discussions about it.)