Jessica Simpson 'Is Going To Tell All' About Ex John Mayer In New Docuseries: Source

Grab the popcorn, things are about to get exciting! Jessica Simpson's deal with Amazon Studios to executive produce a “fictionalized” series based on her life has lot of people in Hollywood terrified — but no one more than her ex-boyfriend John Mayer, OK! has learned.

“Jessica plans to tell the truth. There were so many executives that didn’t believe in her. So many old, white men that told her to be a second-rate Britney Spears, rather than a first-rate Jessica Simpson. Even after she was the most famous person in America, John Mayer tried to change her, and he succeeded for a while. Jess is going to tell all,” a source exclusively tells OK!. “John didn’t do right by Jessica. He thought he was smarter and treated her like a dumb blonde — now that dumb blonde has a multi-million deal with Amazon."

Insiders add that it is going to be a blast seeing who Simpson casts to play him. “I hope they hire an actor that shows what John looks like on the inside, not the outside. He must be dying that Jessica got the last laugh,” adds a pal.

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The fictionalized coming-of-age series starts when the singer is in her mid-twenties, but so much happened in her life after that, they will get to Nick Lachey, Mayer, Adam Levine and Justin Timberlake in season 2, the insider dishes.

Earlier this week, it was announced that the 40-year-old would work on two TV shows — one unscripted and one scripted — which would be based on the blonde beauty's best-selling memoir, Open Book.

"I am humbled and honored to partner with @amazonstudios to bring my story and heart to life on the screen and executive produce a fictionalized coming of age series about my mid-twenties, a new intimate unscripted docuseries with music as a key component and 2 essays where I will share my soul and perspective while holding your heart close to mine," she captioned a photo of herself laughing in front of an Amazon sign via Instagram.

"I am a huge TV fan and many of my favorite shows live on Amazon, so the gift of this unprecedented collaboration is the brightest visible dream for me. From our first meeting I had a visceral connection to every member of this team. I know that parts of my life have been extraordinary, but I also know that many of my struggles are universal. I hope to continue the mission I set out to accomplish in writing Open Book — to inspire others to be entertained, moved, and empowered to walk through fear and come out on the other side even stronger," she added.

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The author — whose book was released in February — concluded her lengthy post by thanking her "family, team and new family members at Amazon" for this amazing opportunity.

In her tell-all book, the "With You" songstress dished about her prior relationships — specifically how she was so drawn to the Grammy winner. “The connection was so strong and made me feel seductive, and he spoke about sex and my body in a way that made me feel powerful, at least physically,” Simpson wrote. “He studied every inch of my face and body.”

However, Simpson was angry when Mayer talked about their sex life in a 2010 Playboy interview, where he called her a "sexual napalm."

“He talked about me by name in the most degrading terms. You can look it up because I had to be asked about those quotes in every interview I did for about two or three years,” she wrote.

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That comment was the straw that broke the camel's back and "made it easy" for her to "walk away" from Mayer for good. "He was the most loyal person on the planet and when I read that he wasn’t, that was it for me," she explained. "I erased his number."