I hear you. Esther Perel's take on affairs might come off as morally questionable to some. She tries to dig into why people cheat without labeling it as strictly good or bad, which can rub people the wrong way. If the book seems like it's pushing that mindset, I can see why you'd skip it.
Everyone has their own limits and views on what's acceptable in a relationship, and it's important to stick to what feels right for you.