One other very powerful and helpful book, from a different, but equally effective point of view is the well-received:
With these two wonderful authors in his corner, breaking up and recovering will be so much easier.
These books will help him find the motivation and the words to begin the process, get through it, and get past it knowing he did the right thing.
I wish him great luck and shall keep him, and you, his great friend, in my prayers.
Elliott, MAE, LPCC, NCC, CCMHC