i tried that book -it was useful, but also glossed over the areas of "what is remorse? how do i know if I'm feeling it?" and "am I really committed? what does it mean to be committed?"
no one, and I mean, NO ONE has addressed these two topics in all of the literature I've seen on marriage, infidelity, and divorce.
Remorse is being sorry enough about what you've done, that you will never do it again. Because you understand in your gut and in your spirit, the pain that you have caused and because of that understanding, your infidelity has now crushed YOU.
That should also sum up your question as to what committment is.