This was helpful for me in teaching me to let go of any expectations or judgments I have about my loved one leaving her abuser, and instead learn to be a better friend to her--so that she can leave him if she chooses to leave, or she can have me as a source of support and safety if she chose to stay.
I had an "aha moment" when this book talked about how my insisting that my loved one leave the relationship, and badgering her about it, was precisely what the abuser does to her--tries to exert power over her and control her actions, and implies that she cannot be independent and is not capable of making her own choices.
The book helps you to let go of your old goals for your loved one and form new, healthier ones that you have control over.