To be honest - I thought this book would be something completely different that I have found it to be. I was hoping for a book about the critical thinking. This one is a book about the job of critic (think art critic) and the background, education and philosophy around.
Taking my misconception into account - my opinion is that this book is ENORMOUSLY prolonged and full of unnecessary facts and data. Good editor might make wonders here.
The book contains some self-given interviews and quasi-philosophical chapters - and in my opinion just the interview would do the work: to understand how necessary and how difficult the concept of criticism is. How much education, taste and thinking you need to do it right - and how some people will still disagree (and they are very well entitled to do it).
Read this only if you are serious about the job of art critic/art journalist, and please read other sources, too.