What's New in Java 7 by Madhusudhan Konda provides a survey of some of the important updates and changes made in the Java 7 release. As the author states this is a survey and not a complete list of all updates and changes. The topics that are covered by the author are done well and provide great examples for the reader to follow. I hope that there might be additions made to this book that cover the other updates and changes that have been made in Java 7, for example Java SE 7 release now contains JAXP 1.4.5, some interesting changes have been made to security enhancements, important enhancement for multithreaded custom class loaders that were prone to deadlock has been fixed, and many others.
Again, I understand that the intent of this book is to provide a survey of some of the important updates and changes ( not all of them ) and the author has accomplished that well. I just think the author could have expanded the survey a bit more and covered even more to make this book a great book to buy. I really enjoyed reading the few topics that were covered and wished that there was more.
Therefore, if you are looking for information on the specific updates and improvements that the author covers, then this book would be good to get. Otherwise, I would just look at reading online the features and enhancements that are made to Java 7, which you can also follow their tutorials. To leave it on a more positive note, I want to reiterate that I feel that the author did a great job on the few topics that were covered in the survey.
If you get the book for free, then enjoy the read. Just don't assume that this is all the Java 7 has to offer.