The purpose of the book is spelled out on the back cover: to help programmers communicate with other programmers through their code. Wherever I found a common problem with several reasonable solutions, I picked the one that communicated most clearly. Many of the patterns have code examples, some from real code and some from invented examples.
Does that answer your question?
Kent Beck Three Rivers Institute
Author of <a href="http://www.amazon.com/exec/obidos/ASIN/0596007434/ref=jranch-20" target="_blank" rel="nofollow">JUnit Pocket Guide</a>