The title of this review does subtly let you know that I think this purchase really might not be worth it. For a start the book's function is mainly to serve as a reference for Pattern training. But in this it is flawed in two ways: First, as someone has already mentioned, it contains mistakes (though this might have been edited out in the latest edition which I have noticed is on sale). Secondly, all of the information that the book claims to sell is available free online anyway. So there is really nothing new or interesting contained within the pages of this text.
The book also contains a section on Tae Kwon-Do's history, which is not just innaccurate and vague, but a complete fairy-tale. The section on board-breaking (destruction) gives little more than pictures showing people doing it. And so it continues...
Unfortunately, given the above, I cannot think of a single reason to recommend this book to anyone. In my opinion there are far better alternatives either free online or for sale on this site, and I would suggest looking into them.