Billy,
The Appendix discusses the SOLID principles of design. Instead of placing an emphasis on how to apply OO design principles, the book focuses more on "where" to apply OO design principles (i.e., the seams of the system). There are plenty of examples that show good OO design in practice, but I don't always explain the OO concepts applied (i.e., different patterns and practices). Instead, I tend to focus on how the OO design concepts help us design more modular software, such as to decouple modules. The Introduction (available for download with link below) explains this pretty clearly.
Visit the book's website at
modularity.kirkk.com where you can review all 18 patterns and download an excerpt of the book. There is also a
mobile web application available that you can take with you wherever you go.
--kirk