Complex sentence: Laura's Diary is due to be published in a book on the 30th of November 2006 because Mills had joked that because Laura was "unlucky in love" he would make it his mission to help her.
Split into simpler sentences: Laura's Diary is due to be published in a book on 30 November 2006. Mills once joked that because Laura was "unlucky in love" he would make it his mission to help her.