"Sullivan is in many ways an arch-Republican. He was very conservative on almost every issue except for gay rights," she says.
"What was eye opening in conducting all these interviews was that so many of these people make me scream at the television when they appear on it - but I also found this deep emotional connection to them in person when they talked about what it means to them to be Catholic, and how important their faith really is to them."
Sullivan told her about his experience of being an Irish Catholic growing up in England. He was ostracized because of his religion and that made him, he told her, embrace it all the more. It was a hard fought thing, and not something he would now ever consider giving up, although it has harsh things to say about his life now.
Says Kennedy, "There's a wonderful commonalty that we don't often talk about which we share as Catholics, that's something I want to get across and celebrate. One of the things that surprised me about this book was how often I found myself laughing. Nancy Pelosi, speaker of the House of Representatives, told me that when she was a girl she only wanted to be a priest. The nuns, she said, were wonderful but the priests held all the power."
Another vivid tale in a book full of them involves actress Susan Sarandon. When she was seven years old she received rosary beads from her aunt.
What she didn't know was that they were glow-in-the-dark beads. When she went to bed that night she turned off the lights and noticed they were glowing brightly. She thought she was having a vision and she began to panic. She was certain she didn't want to be a saint.
Celebrated author Frank McCourt also told Kennedy of how back in Limerick he would leave confessions on Saturday evening feeling like he was walking on air. In America they told him that for the same experience he should try therapy instead.
An atheist, McCourt told her simply, "I'm reconciled to the oblivion that is coming."
Faith and the absence of faith are both journeys, and Kennedy's provocative and thoughtful book hears from them all.