The `Firework` hitmaker - who is currently dating John Mayer - is expected to discuss in detail her 14-month marriage to British comic Russell Brand in the tome, which will be called `Part of Me` because she wants to put out her side of the story before her former spouse releases the next instalment of his `My Booky Wook` autobiographical series.

A source told The Sun newspaper: "Several publishers have been after Katy for a while. She decided to go ahead so fans don`t have a one-sided story when Russell publishes another `Booky Wook`."

The news comes weeks after Russell - who has written two books about his life, `My Booky Wook` and `Booky Wook 2: This Time It`s Personal` - confirmed he was discuss his relationship with the pop star in his third literary offering because he knows he can`t ignore something that was such a huge part of his life.

Russell - who split from Katy in December 2011 - said: "I will write more Booky Wooks, I love writing those Booky Wooks and there`s a lot to cover. Maybe I`ll wait until I get married again or have more children before I write any more.

"You can`t write things about your life and not include things that happened in your life."
sections: Celebrities