Hi mswc101 - I'm not sure what a good book would be for that, either. I did some internet searching, and the closest thing I could come up with was a book I found that got some good reviews on Amazon, called, "Take the Bully by the Horns: Stop Unethical, Uncooperative, or Unpleasant People from Running and Ruining Your Life" by Sam Horn.
The Publisher's Weekly review of this book does say that it has at least one example of infidelity in it:
Horn's example situations include spouses who hit or cheat, spouses' bosses who grope, coaches who berate, false friends who cajole confidences, business partners who steal, neighbors who instill fear and people who chronically hit up family members for bail money (or "deja moo"). Role playing "Action Plans" for conversation help firm up psychic independence and avoid pointless, draining argument.
I've not read it myself. Hoping others come along with more experience. If not, there are many members here to help you with advice in the different forums here on this site.
Best of luck to you!