The book reveals that Shane's years with Liz were the "happiest years of my life", as rumours swirl that the spin king and actress have rekindled their relationship.
The pair first met in 2010 in a private box at Goodwood Racecourse in England and experienced an instant connection. At the time of meeting, Shane was attempting to reconcile his relationship with his now ex-wife Simone Callahan, while Liz was still married yet estranged from millionaire businessman Arun Nayar.
While Shane has claimed "nothing happened" between them when they first met, he officially split with Simone later in the year after a string of flirtatious displays with Liz on social media. When Shane and Liz were photographed kissing on the streets of London, their 'secret' relationship was finally outed. These photographs signaled the end of Shane's reported reconciliation with Simone.
Shane, 49, proposed to Liz, 53, after an intensely loved up 18 months together on an "impulse" as they partied on the dancefloor of close friend James Packer's superyacht.
According to news.com.au, Shane wrote in his biography, "I was more in love with Elizabeth than I'd realised I could be," and that he missed the love they had as his years with her were "the happiest of my life."
"Completely on impulse in the middle of a dance, I grabbed Elizabeth, dropped to one knee and said, ''I'm not sure about you, but I've never got along with any woman as well as I get along with you. I'm madly in love with you. Our kids get along great. How would you like to spend the rest of your life with me?''' wrote Shane in his book.
"Without hesitation, she replied: "Of course I would, silly, I'm madly in love with you too. I feel exactly the same. I've never got on better with anyone than I do with you either"."
News of their engagement broke a week later and the press went crazy for it. However, the pair were furious that they couldn't break the news to their children themselves and blamed Packer for leaking the story.
Shane revealed in the autobiography that when he confronted him about it, Packer responded with, "Okay it was me...I'm sorry. Hit me, do whatever you want."
The couple quickly purchased a home together but split in 2013.
"There was no single, clear reason why our relationship ended," wrote Shane.
He claimed that the couple may have gone their separate ways due to Liz's new role on The Royals alongside her ex-boyfriend British actor Hugh Grant, who she had previously dated for eight years.
"The more you're apart, the more you ask questions," Shane wrote.
"I got jumpy about the time Elizabeth still spent with Hugh Grant… he is her best friend but they saw each other more when I wasn't around so, well, you know."
"We still love each other in many ways — we're not in love, like we were - but I still care for her deeply,"
"I think we were good for each other."
Shane's new book No Spin is available for purchase now.