Spencer Pratt Writing Tell-All About Ex Heidi Montag

Credit: Steven Lawton/FilmMagic

Spencer Pratt is ready to tell his side of the story.

The Hills villain, 26, tells UsMagazine.com exclusively that he is penning a tell-all about his relationship with ex Heidi Montag, including new details about her tormented relationship with her mother, Darlene Egelhoff.

"My last book, How to be Famous, didn't make the New York Times best-seller list because it was in the self-help section," Pratt tells Us. "This one is going to be totally different. I'm not holding anything back."

Montag is none too pleased, telling TMZ she may take legal action to stop him. "This is exactly why I left him," she said. "Right now I'm looking into my legal options."

In July, Montag filed for divorce after one year of marriage, citing irreconcilable differences. Their divorce is expected to be finalized on Valentine's Day of next year.