I'd say the definitive book on the subject of Unit Testing and Automated Testing. Very thorough, comprehensive, and easy to follow.

Early failure, Lessons learned

Surprisingly, one of the best insights I got from Roy was within the first few paragraphs of his preface. He shared about an early experience of a failed project that I believe is worth passing along. This project started off with great automated testing enthusiasm, in a fully test-driven manner. Unfortunately all the great number of tests written became "a daunting task" to change as requirements and designs in the system changed, and the tests themselves were brittle. In his words:

The project was a miserable failure because we let the tests we wrote do more harm then good.

Since that project, Roy has been compiling 'best practices', and this book is a culmination of those lessons learned. I very much appreciate his transparency here, and set a mind-set for me that I carry into all projects: Automated Testing is valuable: But ensure the tests remain flexible and easy to maintain.

Again, and excellent book; highly recommended for anyone getting into Automated Testing