Simpson has been busy this week promoting her memoir, Open Book, which revisits her early 20002 marriage to Lachey and the reality show that they co-starred in. "I don't believe that the show is what tore our marriage apart," she told Buzzfeed's AM to DM. "Nick and I were very great at being together publicly and on-camera. We were best at our relationship when we were singing together. I felt like we were at home in that place. But as far as doing the reality show, we just kind of had fun with it until the end—until we started having marital problems."