The info is still relevant. While the examples may contain usage of
deprecated code, it's easy to figure out how to update it. For one,
some examples have been updated to use either 1.5 or 1.6 of GWT.
Most of the deprecation usage comes from the change from
EventListeners to EventHandlers. Also, some places where you used to
add "annotations" in the javadocs have been replaced with real Java
Annotations.
The book is pretty good aside from going over how you would unit test
your apps.