Hi there TSquared2 and WenikiTiki. I've just started reading Codependent No More as homework from a therapist.
I started counselling with my ?soon-to-be-walk-away-wife? I found some of the advice a bit harsh, too, but in the main the idea of "lovingly detaching" and GAL are there, similar to Divorce Busting.
My first therapy session with my wife was awful: felt like I was being ganged up on; my wife dominated the conversation and made sure certain things didn't get revealed in the alloted time. Therapist seemed rather dismissive of my feelings (as having 'typical' response to being cheated on.)
But then I went to see the counsellor on my own, filled in the information that didn't get covered in the couples session and what she said was eye-opening: my wife has an 'Love and Approval' addiction... hungers for outside validation. This has manifested recently in serial cheating (sort of), but there have always been signs (spending $ recklessly on the salon and clothes, working till all hours to please the bosses, jumping at any/every possible social invite, etc.) She assigned me Co-Dependent No More, and initially I thought it sounded like 1980s psycho-babble. BUT reading it made me realize there is an addiction and I have been enabling it: backstopping her financially, jumping in to pick up the slack where she neglected household and childcare duties in favour of social and work stuff.
I think there's value in the concept and in the book. Like I said, I do see some common themes with Divorce Busting.