Cheryl, who is best friends with Kimberley after finding fame together in Girls Aloud, also comments that some parts of the book - called A Whole Lot Of History - came as a surprise to her.
She says: "Amazing! There are things about Kimberley's life in here that even I didn't know."
Singer Kimberley signed the deal for her autobiography in April and promised that it would be jam-packed with tales of the highs and lows of her life.
Speaking at the time, she said: "People have been asking me to tell my story for years but it never felt right while the band was still together.
"Now, as we all turn the next page in our lives, it feels like the perfect time for me to share with my fans what my life is really like."
Fellow BFF and Girls Aloud star Nicola Roberts has also had a sneak peek at A Whole Lot Of History and admitted she "cried and laughed" throughout.
Kimberley's book goes on sale on 26 September. Until then, check out this blast from the past Girls Aloud video!
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