I picked this up because the title made me laugh. While the authors do hasten to say that laying blame is not useful, overall I still think they overstress "nurture, not nature." While they sometimes obliquely recognize that two people in similar situations react differently, they also argue that "Personality is Experience, Internalized." As a parent of five kids, I don't think it's that easy. One of my kids was essentially a cheerful, low-maintenance optimist from birth; another seems to be equally cheerful and low-maintenance and an optimist now she's a teenager, but she was much more grim and much higher-need as a child. Those in-born personality traits can have a big impact on how the child responds to childhood experiences.
The authors also present relationship problems as just two people who aren't meshing well, who are inadvertently pushing each others' buttons and triggering issues from their respective childhoods; while that's certainly what usually happens, there's also the fact that some people deliberately choose to control the relationship. I've heard that couples counseling is not a good option if you're dealing with an abuser; reading this book I can see why that might be.
Not to say that the book doesn't have some interesting insights and some good advice. Just that it's pretty average, IMHO, rather than something I'd recommend.