This book contains Edward de Bono's thought on our current system of thinking. He believes that our current system of thinking is excellent, but not enough. He believes we focus too much upon judgement, rather than exploring a subject. He believes we focus too much at looking back to the past rather than designing a way forward.
These are all points with which I wholeheartedly agree. So why did I give this book a low rating? I've only read a few of de Bono's other books, however I can already state that 75% of this book was a rehash of older works. The book is very repetitive, and on numerous occasions he offers the same examples over and over again, albeit in different sections of the book.
How about the 25% that I hadn't seen before? Well, although there is new material, he covers it in a cursory fashion. He offers some new notations, some suggestions for design although I can't see any way to apply these to my thinking. If you haven't read any of de Bono's other books, then go grab them now! If you have read de Bono's other books, then you have already read this one. In summary I can't really recommend this book to anyone.