Gregg:
Thanks for bringing up an interesting topic.
Online resources are great and the benefits are obvious: They provide free, timely information on demand. But, they can have their limitations. For example, the Web is a wonderful, but chaotic place. Sometimes it is difficult to get a truly organized understanding of a topic by relying only on online content. Sometimes knowledge gaps are created. Moreover, sometimes you don't realize that those knowledge gaps exist until one gets you into trouble. Also, sometimes the quality of the content is unknown. We have all seen wrong information bounce around the Web.
The benefits of a book differ from those of an online resource. A good one presents an organized discussion of the topic. It shows how all the pieces fit together. Also, all the major publishers subject their books to full peer reviews. Thus, you can have a fairly high degree of confidence in the quality of the information in a book. Remember, books are costly to write, edit, and print. Because the time, effort, and cost is so great, publishers and authors go to great lengths to ensure the accuracy of their books. The same cannot be said for all Web resources.
You ask specifically what my book
Java 2, v5.0 (Tiger) New Features offers that you can't find online? I would answer in part by saying "Depth of coverage, cohesion, organization, and continuity." I would then add that it puts all the new features of Java into their historical perspective, explaining both "the how and the why." The book also shows how the new features work together in many cases.
Hope this helps!