What's it like these days to be the people who wrote the book on the science of nonmonogamy? The New York Times best seller Sex at Dawn was published four months ago, and since then, coauthors Christopher Ryan and Cacilda Jethá have received a lot of attention for their book. It's not surprising—Ryan and Jethá have woven physiology, archaeology, primate biology, and anthropology into a controversial theory: Humans are not naturally inclined to be monogamous. People can choose to be in lifelong monogamous commitments, but long-term fidelity is difficult for Homo sapiens.

The notion that most folks in monogamous relationships feel attraction to other people, even if they don't act on it, doesn't seem like new, shocking information to me. But it's an idea that troubles some people, and when I sat down with Barcelona-based Ryan on his recent visit to Seattle, he told me how people's emotional response to the book is creating a subtle kind of censorship.

"It's been a real roller coaster," Ryan says. "The state of publishing now is so dysfunctional. There's been extreme enthusiasm from the readers, but our publisher still isn't pushing distribution of the book. I've been to six big bookstores here in the States and still haven't found our book in stock! It seems maybe someone at HarperCollins isn't into the idea of the book, or the buyers for the big chains aren't into it, so there's resistance somewhere between where the books get printed and the people who are trying to buy it. I think there may be some Christian-fundamentalist craziness somewhere along the line holding back widespread distribution. Most of our sales are through Amazon. This book tour I'm on—we're paying for this. Our publisher didn't support the idea. Eventually, after we arranged free national media support and booked events from Seattle to Manhattan, they agreed to throw in $500. So mainstream media is very enthusiastic, but our own publisher is pretty lackadaisical about it."

Is it possible that some of the book industry's internal ambivalence arose because Ryan and Jethá did something uncommon in books about the psychology of sex—they refused, even under pressure from editors, to give any how-to-save-your-marriage advice? Ryan agrees. "Cacilda and I very consciously decided we weren't going to write a prescriptive book. We're resistant to giving advice without knowing people. People and relationships are so complex—we don't have much patience for cookie-cutter, one-size-fits-all advice."

It's easy to tell Ryan has been living abroad for 20 years. I laughed and told him, "Oh, no, this is America. We don't do nuance and context here. Our sex, our politics—everything is black and white."

I asked Ryan about what their next book might be, and he said, "We're thinking about a survey book, a study of the way different people around the world integrate long-term emotional intimacy with erotic intimacy. At this point, I'm thinking self-publishing might make a lot of sense."