In my opinion, Phil Gordon is the best poker writer out there. He writes in a straightforward, clear language, which is really easy to follow. I've read all his previous three books and also his DVD, and I was really afraid that he had given up writing, since his previous book was released five years ago. I am glad to say that Phil Gordon is back, and in better shape than ever.
In his private life, Gordon had gone through a quest of improving his own game, since poker players have evolved quite drastically in the past few years. And it is rare to see a poker expert publicly admitting that he had to step back and re-study the game. The Gold Book is the result of this quest.
The book starts with lots of math that will make the head of most readers to spin. But don't give up. Soon enough things will get clear as the author shows tools and techniques that will for sure improve your game. While some of them were already featured in the author's previous books (such as the "squeeze" play, a.k.a. "fish'n'chips"), this time he explains more in depth the math behind them.
This is a book that you will have to re-read several times to be able to get everything it has to offer, especially as your game improves. In the end, it will make you to completely re-think your game. And that is why this book is so good.
The only "negatives" I can see with this book is that this time the author didn't put a lot of jokes in the text. You see, the typical Gordon jokes inserted inside the book (e.g. "feeling like the time I had bad shellfish in an all-you-can-eat buffet in Kansas City") help me to memorize the concept he is explaining. Also, even though there is a chapter with some hand examples, I'd prefer to have some real examples after each concept is explained. He did that here and there, but I wanted to see more! I hope Phil Gordon writes a follow-up book only with real hand examples, just like he did with his Blue Book.
On a more serious subject, for a book released after "Black Friday" and the demise of Full Tilt Poker, I think the author should have re-vamped the parts he talks about online poker and Full Tilt in particular. For example, he mentions that Chris Ferguson was able to create a $126,000 bankroll starting from zero and that Phil Galfond also has accumulated an on-line bankroll of same magnitude, but didn't say anything about what happened to player's online bankroll after "Black Friday."
BTW, around 20% of the book is dedicated to PLO (Pot-Limit Omaha).