I've just finished reading "Developing RESTful Services with JAX-RS 2.0, WebSockets, and JSON" from Packt Publishing. It's an interesting book, mostly because the authors provide plenty of context around the technical explanations and give a good overview of the covered technologies.
WebSockets and Server Side Events are two new features provided with JEE 7 that will allow you to develop client (browser) / server applications that benefit from server side 'push' communications. This book explains both of these, also the previous generation answers to this problem (Polling, Long Polling) and examples of all of these. Throughout the book, sensible diagrams are provided that help the reader understand things. Truly, a picture is worth 1,000 words. Too many technical books fail to provide enough useful illustrations, I'm pleased to report this book is not one of them.
Ancillary features (i.e. Bean Validation) are given coverage. The authors spent an appropriate amount of time on these-- where things don't require a lot of text, not a lot is given. By the way, the whole book is just a little over 100 pages, so it's not a long read. But those 100 pages are generally well written ones, so this book still represents good value.
REST is also explained, including the new client API. REST seems to be picking up steam, so if you're not well versed in it yet you might have a look at this book for that purpose. Hand in hand with REST goes JSON, and this book also explains how you can produce and consume JSON documents in Java.
All things considered, this book is a good, targeted resource that delivers on it's promise. I imagine I'll be using it as a reference resource from time to time.
The book can be found here.
Happy (RESTful) Reading!