Defensive programming is not a new idea but has been around for 30+ years. This book applies the tenets of it to database programming to produce more robust code that is safe to run in unexpected situations.
The subject of this book is to some degree also covered in other books on SQL development, where authors usually recommend to avoid 'risky' practices that might unexpectedly break one day, e.g., after an update of server software. However, it's usually not covered at depth because it's a rather special subject that will mainly appeal to expert developers who have already mastered all the basics of SQL and database programming.
The book focuses on a special, advanced subject, and therefore it is most useful for experienced SQL developers. In it the author looks into a number of typical pitfalls that most SQL programmers will experience the hard way one day in their careers. He offers valuable, practical advice how to avoid these pitfalls before they hurt. The text is well-written and clearly the author knows the subject very well and has significant experience in the field. Some of the practices highlighted in this book and discouraged as 'potentially risky' by the author are of the type that a 'good' programmer will not do anyway. As I myself know only too well often this is more inspired by gut-feeling than really solid knowledge, experience or systematic experimentation.
This book fills the gap between gut-feeling and knowledge in selected areas of SQL development by pointing out why the gut-feeling is indeed justified, why and in what way the practices are potentially problematic, what their impact may be if things go wrong, and how the risk can be avoided and at what price.
In my view the book will be a valuable read for most experienced SQL developers.