We never planned on writing an advice column. Twenty years ago, the creative director of one of the largest U.S. newspaper syndicates saw something we wrote and asked us to submit sample columns. Creating those columns lit a flame. It became the first step in a service project which continues to this day.

After a month passed without hearing anything from the syndicate, we distributed the column ourselves. An hour and a half after sending out a few emails, we had our first newspaper. Six weeks later we were in five or six papers in the U.S. and Canada. Two years later the column was in newspapers in twelve countries.

Before long we were straining to answer all the letters we received. The letters came from musicians and chefs, ranchers and housewives, business people, factory workers, and a minister performing weddings, even as he doubted his own marriage would last. Some letters were full of misspellings; others ended with an imposing title and a corporate address.

Over the years, one group of letters stood out, not simply because there were so many of them, but because the writers’ wounds were fresh even when their injury had been inflicted years before. These were the letters from those betrayed by the person they were dating, living with, engaged to or married to.

The letters followed a predictable course. Though our feelings often surprise us, our emotions follow universal patterns. Betrayal feels like betrayal for a reason, and there are reasons it is so hard to forget.

In Cheating in a Nutshell, we retell stories we were told. None of the stories is exceptional; each is typical of the experience. Many times we balance a story with contemporary research, but the book doesn’t depend on that research. Fads and perspectives in social science change, but the experience of being betrayed does not change.

We wished we could have answered all the letters we received because we knew how much pain the writers were in. Of the many letters we answered, we wish we could have answered at greater length, but there wasn’t time. If we had found a book on infidelity we could recommend, we would have recommended it. But there was no such book, so we knew in time we would write this book.

This book is the longer answer we wanted to give each person who wrote us. Before writing the book, we reread over 3,000 cheating letters from the first 10 years of our column. As we wrote we had three groups of people in mind:

1. Those just learning their partner deceived them.
2. Those who stayed with a cheating partner, and now realize things cannot be restored.
3. Those betrayed in a past relationship, who seek a deeper understanding of what happened.

We hope this book will encourage the next generation of researchers—perhaps now only undergraduates—to take infidelity research in a more accurate and factually correct direction. In Cheating in a Nutshell, we discuss emotional infidelity alongside physical infidelity rather than treating it as a separate topic. We do this because the two share much in common and because emotional infidelity is often only the cover story for deep physical involvement. The damage from each is similar. Beyond that, emotional involvement is at the center of all our relationships. Admitting to emotional involvement may make the betrayal even worse.

Last, let us say, if we have a point of view, it is because the facts point in one direction. We cannot find a way to make the case for a different point of view. In The House on the Strand, a novel by Daphne du Maurier, the main character is a man named Dick Young. At one point Dick says, “Truth is the hardest thing to put across.” We agree, and we would define truth as that which corresponds to facts. Truth is not what we wish to be true or what we would hope to be true. Truth is what corresponds to facts.

Thousands of people wrote us. They had a story to tell. This book is the explanation of that story.