I think this book is very helpful. It is easy to read and gives good advice, which would be applicable to reading all sorts of books, not just the bible, though it focusses particularly on understanding the bible.
But there is one thing missing, and it is a huge oversight, I think. The bible is about Christ. You could conceivably miss this in reading the Old Testament, but it is, I hope, glaringly obvious in the New Testament.
The book gives many sensible tools for unearthing the riches in the bible, but never mentions the fact that you will fail to understand the bible and miss its message if you don't ask yourself, how does this part of the bible relate to Jesus Christ and God's plan to reveal himself to the world through him?
I think this should be tool number one in the next edition of the book.