I'm always reluctant to discuss a book without having read it first, but glancing at those reviews and the synopsis my first impression is that this is just yet another way to tell women that they can have it all if they just do x, y, z (i.e. tips for how to get on in a patriarchal society).
There's been a lot of research to show that attractive charismatic people tend to better in life. I don't actually have a problem with any book coaching someone how to make the most of those skills. My concern would be with the value and importance based on those skills. Inter-personal skills are valuable. A well-groomed appearance can be too. That doesn't necessarily mean that the presence of both qualities in spades mean you are a decent person.
Also, I wonder if the book deals with the fact that erotic capital may give you more negotiating power in various social/professional situations but can it help with other things that particularly effect women? Such as:
How does erotic capital help the working mother deal with childcare issues?
How does erotic capital help the SAHM keep some degree of independence?
How does erotic capital help a woman get her H to stop beating her?
How does erotic capital help a woman pass an exam (which is marked blind)?
How does erotic capital stop a woman getting raped?
It just seems to be another way of placing responsibility on women to fit in with our cultural norms instead of recognising that some of our cultural norms are inherently unfair to half the population and maybe should be changed for the good of all.
But admittedly I haven't read it.