I would beg to differ on the "concenting adults" point, but I don't have any data to back that up.
From the research I am giong through I am finding the most knowledgable marriage scientists who have studied affairs find them an addiction much like gambling or substance abuse. The concept of consent isn't relevant in that context. The person is seen is "ill" rather than simply a consenting adult in love with someone other than their spouse.
I own after the affair and four other infidelity related books. Not just friends seems to be the best one in my opinion.
Penny Tuppy argues that all affairs save the one night stand type are addictive in nature. My that she means that these experiences fire off chemical charges in the brain that cause the person to lose their capacity for good judgement and they become increasingly dependent on the fantasy of the affair to cope with their life.
Gradually their real life begins to fall apart while the affair increases in intensity. Eventually something gives - either the affair ends or the marriage does. Penny calls it "the great race".
I just dont' find many counsellors with a lot of good background in the subject. The weathering isn't my concern it is my spouse leaving. I can stomach an affair, i can't stomach having this person rape my home, violate my marriage, and sex my spouse up into abandoning me. This to my mind should be handled as criminal behavior.
If my marriage ends, I want it to be more civilized than this nightmare.
The good counsellors who actually list affairs explicitly in their services often group it with substance abuse, gambling, or other destructive and addictive behavior.
I have never looked at affairs as tragic love stories, despite what hollywood tries to sell them as. Its' just hard to find a professional who handles them for what I believe them are.