It's all about RESTful services nowadays and that's the main goal of this edition.
So you will be reading about JSON, JAXB, SOAP, annotations with Jersey to fastrack development and many other features.
To complete the world of web APIs, the master language is XML so be prepared to see many elements and attributes around ;-)
This is for the fun and descriptive part.
The less funny part but respectful and required is about Security, adn SSL protocol (httpS://...).
I would recommend this easy-to-read and compact useful descriptive guide that will make you understand the underground of the web services with Java using technology.
The book can be bought at http://shop.oreilly.com/product/0636920029571.do.
Disclaimer: The book was given as part of the blogger review scheme from O'Reilly.