Spencer Pratt

Spencer Pratt is giving the author thing another whirl — this time at the expense of Heidi Montag.

The 27-year-old Hills villain tells Us Weekly that he is writing a tell-all book about his estranged wife with new details about her relationship with her mother, Darlene Egelhoff.

Goodbye, Speidi: Heidi Montag files for divorce from Spencer Pratt

"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 the magazine. "This one is going to be totally different. I'm not holding anything back."

He did not name a publisher.

Montag, who filed for a divorce last month after one year of marriage, has since expressed her anger about the planned tell-all.

"This is exactly why I left him," she tells TMZ. "Right now, I'm looking into my legal options."

Calls and emails to Montag's lawyer and Pratt's rep were not immediately returned.