Nick Cannon has signed and sealed a deal to write a tell-all book about his marriage to Mariah Carey -  and she is furious about him betraying her. Mariah rejected Nick's numerous demands for a $30 million divorce settlement so now he's writing the book — saying he plans get his payday for being married to her one way or another - and there is nothing she can do about it because he already signed the deal last week with major publishing company Simon and Schuster. Simon & Schuster has confirmed to Daily Mail Online that the book is being published by Gallery Books, an imprint of the high-powered publisher. 'Mariah was willing to give Nick $10 million but he said 'hell no' and demanded $30,' a family friend tells the Daily Mail exclusively. 'Mariah says it is what they agreed to in the prenup before they got married. Scroll down for video . Battle of wills: Even though they have a prenup that would pay Nick $10million, Nick wanted more. When Mariah refused he decided to get his payday through a book deal. But Nick insisted he needs and deserves more than what they originally talked about, but Mariah wouldn't budge. Now Nick is being very vengeful, dating other women in public including Nicole Murphy, Michael Strahan's ex, the source says. 'Mariah kept telling Nick she was not going to give him a penny more than $10 million,'  says the friend. 'He told her he could write a book and get $30 million and much more for a movie deal for all of the crap she put him through over the years. 'Mariah told Nick nobody cares what he has to say and told him to take it or leave it because that's it - not a penny more.' The friend believes Nick asked for an outrageous amount from Mariah so when she said 'no' he could use that as an excuse to go to the book publisher. Nick hardly needs Mariah's money- although she is worth more than ten times his value. The actor and host of America's Got Talent has an estimated net worth of $20 million. Mariah is worth about $225 million. The estranged stars have been going back and forth about this since Nick filed for divorce in December. He was finally tired of arguing with her. ''He says she is being unreasonable so he has to do what he has to do. 'Now Mariah is angry, devastated and scared that Nick will reveal her inner most secrets and make her look like a desperate fool.' Mariah was crazy about Nick and trusted him with everything in her life but, now she feels he has turned out like every other man in her life and she is completely crushed, the friend reveals. Mariah, 45, and Nick, 34, have been battling about money and custody of their twins since he filed the divorce papers four months ago and even though there is a prenuptial agreement Nick is willing to air their dirty laundry — for a big fat check. US singer Marih Carey and her husband, US movie maker and actor Nick Cannon, leave the hotel to have a dinner at the Eiffel Tower in 2012 to celebrate their fourth wedding anniversary . Battle for the babies: Who gets custody of twins Monoe and Moroccan Cannon is another issue in the divorce battle . Mariah and Nick were married on her private estate in the Bahamas on April 30, 2008 and they welcomed their twins Monroe and Moroccan on April 30, 2011. However, in August 2014, Nick confirmed that he and his wife, Mariah had been separated for a few months and he filed for divorce on December 12, 2014. 'Nick says he is going to tell the world about Mariah's drug use, her strange eating habits, psychosis, what she has said about other artists, her sexual proclivities and her parenting skills. It which will really be hurtful,' the insider continued. 'And Nick is also going to explain why he thinks he should have full custody of the twins. Mariah has admitted she never wanted children and Nick is going to tell the world why she felt that way. 'If Nick was not willing to spill all of their nasty and salacious secrets he would not have gotten a book deal. So obviously, Simon and Schuster feel this is going to be a blockbuster and they signed him up.'
Nick Cannon has demanded $30M to settle his divorce from Mariah - even though their prenup calls for less . Mariah has refused and now Nick has inked a deal with an imprint of Simon & Schuster, Gallery Books . Nick filed for divorce last December after six years of marriage . Mariah and Nick have been battling about money and custody of their twins ever since . Nick to reveal secrets about drug use, strange eating habits, her put-downs of other artists, her sexual proclivities .