This is a book exploring what the authors call 'counter-dependence', though I have heard it described in other ways as avoidance, narcisissm, emotional anorexia, etc. They describe it as the flip side of co-dependence, which is accurate.
In terms of what the book describes, it is useful. It is certainly a real phenomenom and accurately described. It is also very in depth.
However the book makes a lot of judgements about various things which I think are questionable. It makes arguments on scant evidence, such as the level to which it criticises twelve step groups (and some of the things it says about SLAA I have not encountered at all in my own work). I think it is dangerous to criticise such groups inaccurately as they are a lifeline for many and have helped many people - I hope none are put off by this book.
It also makes a number of value judgements about personality, culture and spirituality which I find rather narrow-minded and questionable. Basically they seem to say that 'new age' type spirituality is the only healthy kind and dismiss religion and other ways of looking at the world.
The theory it outlines is detailed, but I am left thinking that it is rather untested and subjective.
The methods it suggests for healing these issues are also quite unusual and I suspect would be beyond many people's taste.