I don't like this book as a book on writing plugins for eclipse for the following reasons:
1) This book's 'exploratory' approach tries to show you how to search (the hack approach) through the installed plugins for excerpts that you can copy/paste/edit. It would have been more useful if the authors used a 'tutorial' approach that constrains the example to documented basics (many different examples that then integrate/or not).
2) As expected (and tiring if you have other book from these authors), JUnit integration is the example developed throughout the book. This may satisfy the need for some types of plugins (code oriented plugins), but leaves much to be desired if you want to develop other kinds of tools.
3) The samples are outdated in 3.0, and the main example won't work/run in 3.0 (even if you download their project source). If you try to follow along, you will quickly be disapointed once you run into that snag. I am sure that under 2.x it works great.
4) This book is useful as a way of seeing a small example built up. However, because of #3, this all becomes useless once the plugin doesn't 'work'.
As with most books that cook a long example as a way of teaching, rather than as a way to support other knowledge, much of the time is spent on explaining how to cook things for the example. For me this doesn't work, as I want something focused that instructs me, rather than a evolving code-walkthrough of a particular example. To me this is boring, and has no use after the initial read.
This book would be great if it was 1/2 as long, and focused on the patterns for the plugins instead, not presume to be an intro to plugin development.