First of all the book is readable. This isn't always true of Go books. The wisdom is mixed in with anecdote which kept me there as I struggled with the topic.
The book is credible - the author does a very good job of "been there made that mistake" which also helped me stay engaged.
Uniquely, in my experience, this book also spends a reasonable amount of time discussing stupid moves and why they are so, which I found to be invaluable. Further I was pleased to get advice on what not to do, e.g., (slightly exagerated for effect) "don't bother studying Joseki, get the principles right" which validated my inability to read even two pages of "38 Joseki".
Before I even finished it the first I think I improved by one stone. Definitely value for money there, then.
It will require re-reading, it is a book to keep by your side, to dip into, gleaning a bit more each time. It's the best book I've ever bought since Iwamoto (which is a great place to start)
Of course, anyone that has previously bought any book called "Fundamentals of <subject matter>" will realise this isn't a beginners book. However, as a self taught player, this one has definitely improved my understanding.