According to In Touch Weekly, the 'All For You' singer is writing the tell-all anthology to help her cope with her sibling's passing.
An insider said: "She is going to talk about Michael's death and how it's affected her and his children and the rest of the family.
"A lot of it will focus on her battle with self-esteem and weight. But that's not always what she has seen when she looks in the mirror."
The source added: "So the book will talk about how she has coped, and about her family relationships. She wants to help other young women out there."
Janet recently confirmed that she has started work on her eleventh studio album.