In "Diary of a Mad Diva," the controversial funnywoman brands the "Twilight" star a "one-trick-pony" before making crude assumptions as to how she became successful in Hollywood.
According to TMZ.com, Stewart's team have demanded Rivers remove the section from the book, or face a possible defamation lawsuit.
However, Rivers has laughed off the controversy. In a video posted on the website, she says, "I'm now being sued by Kristen Stewart. She obviously didn't read our disclaimer, which is it's a comedy book. ... I can't wait to get her to court. ...
"Her lawyer contacted my lawyer, which shows the sense of humor she has ... zero. ... I'm a comedian. I've been doing it for 50 years. If people don't get it ... don't read the book. ... If you're going to take it seriously, you're a fool."
"Diary of a Mad Diva" is due for release next month.