The Other Boleyn Girl (The Plantagenet and Tudor Novels #9) by Philippa Gregory

Mary Boleyn catches the eye of Henry VII when she is a girl of just fourteen.

But her joy is cut short when she discovers that she is a pawn in her family's plots. When the capricious king's interest wanes, Mary is ordered to pass on her knowledge of how to please him to her friend and rival: her sister, Anne.

Anne soon becomes irresistible to Henry, and Mary must resign herself to being the other Boleyn girl. But beyond the court is a man who dares to challenge the power of her family to offer Mary a life of freedom and passion. If only she has the courage to break away - before the Boleyn enemies turn on the Boleyn girls...

Now a major film, statting Scarlett Johansson as Mary Boleyn, Natalie Portman as Anne Boleyn and Eric Bana as Henry VII.