For learning Eclipse RCP, reading a book is not the most efficient way. We can find a lot of free resources on line. Other than programcreek.com, there are a lot of tutorials that are written by experienced Eclipse RCP developers. Here are some learning resource I have found useful.
1. Official document website of Eclipse: Eclipse RCP Documentation
This website is has Java doc for using Eclipse platform and also some tutorial written by those document writer.
A list of extension points available from the platform.
Some articles that serves as "hello world" example.
4. Google Code
Learn Eclipse by reading source code.
<pre><code> String foo = "bar"; </code></pre>