The Ex-Etiquette divorce columnists answer a question about what to tell kids about divorce. Go read the full Q&A, but the gist of their advice is, don't tell even adult kids why a divorce happened. Their reasoning is that a parent can use the "it's never one person's fault" line to teach the kids a good lesson about the hard work that marriage requires.
While I understand where they are coming from, what this advice misses is the effect of this message on the kids. (And, again, we're talking about adult kids here.)
One of the individuals I interviewed for my book didn't learn the real reason for his parents' divorce--his mother's ongoing affair with another man--until well into his 30s. Without knowing the truth about the breakdown of their marriage, he always thought their small bickerings caused the rift; so, whenever he and a girlfriend would begin to argue over small things, he saw doom ahead and broke things off. When he finally learned the truth about his mother's infidelity, his perspective on his father radically changed, and he began to see a new way to approach his own relationships with women.
There are appropriate times and ways to tell kids about things like this. What About the Kids? has some great guidance for parents on this issue. Do kids need or even want to know all the grimy details? No, but this is one instance when the truth really can set us free.