This is an ambitious book as the author tries to argue that all knowledge and experience is reflected in the Enneagram. The book is a presentation and interpretation of the writings of G I Gurdjieff, a Russian philosopher, mystic, spiritual teacher, and composer. His writings are very esoteric and often difficult to understand (according to those who have read them). It may be that Blake, in writing The Intelligent Enneagram, has helped to explain some of these teachings. But even that is unclear.
It is true to say that The Intelligent Enneagram is an achievement. But I'm afraid I don't consider it a great one. The writing is complicated, often opaque, laborious, and filled with jargon. After getting about one third of the way through, I had to give up. There is usually something worthwhile in most perspectives. But they're hard to find in The Intelligent Enneagram because of its writing style.
The other issue is that it is easy to criticise as a work of apophenia -- 'the human tendency to seek patterns in random information'. So much of parts of the book I read seem to be a contrived effort to find patterns and force them into the Enneagram diagram.
The Enneagram has, more recently than Gurdfieff's teachings, evolved into use of the diagram as the basis for a personality profile framework. Blake doesn't mention this anywhere that I can find so I'm not making any comment on that particular use of the diagram. It has its own history which is a separate subject.
Overall, while there may be some aspects of the book that are interesting and clever, it is a drudgery to read it with its complex, convoluted detail. Others clearly have a different opinion judging by reviews of the book. I'll leave it to you if you want to check the book out and form your own opinion. But this one is not for me.