This book gives a practical introduction to PRINCE2. However, PRINCE2 certification is not based on the content of this book or any other, apart from, of course, "Managing Successful Projects with PRINCE2". So, where there are grey areas in PRINCE2, and there are many, the latter book is the reference. The other books may offer sensible advice, but if they were to contradict the reference book, or provide information not in the Reference book, you could end up being right but getting it wrong, at lest as far as the exam is concerned! My advice, if you want the PRINCE qualification, is to get and study the reference book, using a formal training course / trainer. The other books are for after the qualification, when you then need to know how to use the method.