Angelina Jolie is set to sign a book deal worth over $50 million.

The 38-year-old star - who underwent a double mastectomy in February - is reportedly the subject of a bidding war for the rights to her autobiography, and the battle has already hit around $50 million.

"Whoever gets her will be sitting on a gold mine. Her book is guaranteed to top the bestseller lists in virtually every country on the planet and even an advance of that size would be recouped within weeks," a source at one US publisher told the Daily Star Sunday newspaper.

A friend of the Salt actress - who has six children, Maddox, 12, Pax, nine, Zahara, eight, Shiloh, seven, and five-year-old twins, Knox and Vivienne with fiance Brad Pitt - revealed Angelina thinks "the time is now right" to pen her book, and she won't be holding back.

"She has always wanted to do this and believes the time is now right ... She has never known such peace and fulfilment in her life. There are demons in her past but she is in a place mentally and spiritually where she feels comfortable enough to write about them honestly and put them in context. No issues - apart from those that might damage her children's privacy - will be taboo," the insider said.