Political commentators Cokie and Steven Roberts have written about their interfaith marriage before, but their latest book gives a concrete example of how it works. Our Haggadah: Uniting Traditions for Interfaith Families (Harper, Mar.) is a practical, plainly written guide to the Passover seder, the ritual meal at the heart of Judaism’s spring holiday. For Steven, who is Jewish, and Cokie, who is Roman Catholic, the annual feast is an occasion to celebrate the shared values of both religions. Reporter Yonat Shimron caught up with them between book tours.

Q: How did your family seder evolve?

A: Steven: It was very important for us to celebrate all the holidays in our religious traditions. A year or two after we married we moved to the West Coast and we were out there by ourselves. Cokie went to a local temple and bought a seder plate and a Haggadah. But that first year we had a seder friends said there are parts we don’t like. The next year Cokie sat down with a couple of Hagaddahs and typed out her own version. We had that mimeographed and we’ve used that for more than 40 years. It got reprinted at our 25th anniversary seder and we updated it slightly. But the core of the book is what Cokie wrote 40 years ago.

Q: How do you incorporate the interfaith element?

A: Cokie: I feel strongly that you do not dilute the Jewish Passover. But the message of the seder--from bondage to freedom, from darkness to light, from death to life, is the same. The Last Supper was a seder. The rabbis mentioned in the Haggadah were very influential men of a theological school around the time of Jesus. Their ideas, their theology, were key to the formation of the early church.

Steven: We provide readings from non-Jewish sources on liberation, from Caesar Chavez to Sitting Bull to Pope John Paul II.

Q: So, Cokie, you really took the time to learn the Jewish traditions. Is that one of the reasons for the success of your marriage?

A: Cokie: When we were very young and figuring it all out, we said we would honor both traditions in our home. For me to honor Judaism meant I had to go and learn it. The culture was not something I could share.

Steven: I did not grow up religiously observant. My grandfather was never bar-mitzvahed and my father was never bar-mitzvahed. My mother said the first seder she ever went to was organized by her Catholic daughter-in-law. We joke that Cokie’s the best Jew in the family. I know I’m a better Jew because I married a Catholic. That sounds like a contradiction, but it’s really true.

Yonat Shimron is a North Carolina-based reporter who writes about religion.