Most students have probably heard the story of England's King Henry VIII and his many wives. In particular, people have read about the wife that King Henry had beheaded—Anne Boleyn. But few have heard the story of Anne's sister. With only a few scattered historical details available to her, Philippa Gregory has created an intriguing historical fiction about Mary Boleyn, who is, as the title suggests, The Other Boleyn Girl.

The novel begins with the beheading of the Duke of Buckinghamshire, a close friend of King Henry's, whose crime was having publicly stated that the king would "likely die without a son to succeed him to the throne." Thus in the first three pages of this historical novel the tone is set for the rest of the story. It immediately becomes obvious that the young king is beginning to exercise his tyrannical powers; he will not allow anyone—friend or foe—to get in his way; and he is extremely serious about having a male heir. And as readers will discover, the king will do anything to get one.

Gregory takes her readers inside King Henry's court where ladies-in-waiting and male courtiers fawn over both the king and the queen. Their days are spent pleasing the royal couple, helping them dress as well as counseling them. Underneath their friendly façades, however, these courtiers and ladies-in-waiting are scheming. They are spies and manipulating pawns for their families, who are seeking power, money, and fame. In this novel, the two most famous families are the Howard-Boleyns and the Seymours. The main focus of both families is to be the first to give the king his most prized possession—a male heir. What the families do to accomplish this goal creates an intriguing and riveting story.

As The Other Boleyn Girl opens, it is the spring of 1521. The Duke of Buckinghamshire, a one-time close friend of King Henry VIII, is being beheaded for insulting the king by saying Henry will never conceive a male heir.

One year after this scene, it is announced that Anne Boleyn is coming from France to live in Henry's court. The narrator, Mary Boleyn, is excited to see her sister Anne, even though there is legendary competitiveness between the two teenage girls. Their Uncle Howard, as well as their mother, Elizabeth Howard, and their father, Sir Thomas Boleyn, have raised the sisters as prizes to give away in order for the family to gain power. Both girls were educated in the French court of King Francis I to refine their courtly skills. When Anne is brought back to London, Mary has already been married to William Carey, the year before, though Mary is only thirteen years old. The sisters enjoy their reunion, though their older brother, George, often referees their conversations.

Shortly after Anne arrives, her family elders tell Mary that the king has taken an interest in her, and she should prepare herself to lure the king to bed. The Howard-Boleyn family has decided to use Mary to their best advantage. Henry's wife, Queen Katherine, has given the king only one daughter and will soon to old to conceive. Therefore, Henry knows his wife will never give him a son. If Mary is successful in producing a son for the king, the Howard-Boleyn family will have a partial claim to the throne. The king makes arrangements with Mary's husband so Lord Carey will not take claims on Mary and insist that she go to bed with him. If Mary becomes pregnant, the king must be certain that the child is his own.

Anne, though put off that Mary has won the king's attention, tries to help Mary seduce the king. One night, King Henry calls Mary to his room, and their affair begins. Over the course of the next few years, Mary produces first a daughter, Catherine, and then a son, Henry.

In order to keep King Henry's interest in the Boleyn family and not wander to the Boleyn's arch rivals, the Seymours, Anne is told to flirt with Henry each time that Mary is pregnant and virtually confined to bed. Anne is much more cunning that Mary and secretly plots to win King Henry's favor for herself. Anne is also more learned than her sister and slowly becomes one of Henry's counselors. In the process, Henry falls for Anne. She beguiles him, much to Mary's disgust.

Eventually Mary gets over her love of the king and turns her attention to her children. She often leaves the court in the summer and goes to live in the country where her daughter and son are kept by Mary's grandmother. While she is living in the country, she begins to realize that she loves life on the farm much better than the courtly routine. Her only goal becomes to find a way to stay on the farm permanently. However, her family needs her back in the court, and Mary is constantly torn between what her family wants and her own dreams.

As the king becomes more entranced with Anne, Mary is forced to take on a secondary role in deference to her sister. Where Mary once Henry's favorite, she has now become Anne's shadow. The higher Anne rises, the crueler and more selfish Anne becomes. Anne sketches out a plan for the king to rid himself of his barren wife. Through Anne's suggestions, the king declares that his marriage to Katherine was wrong. She was the wife of his brother. When Henry's brother died, he should not have married her, Henry now claims. The proof that the marriage is a sin is seen in the inability of the queen to have any more children. Henry petitions the Catholic Pope in Rome and waits for the annulment of his marriage to Katherine so he can make Anne his wife and queen.

When the pope denies the petition, Henry declares himself the head of the church in England. In this position, Henry can make any laws that work to his advantage. Anne has worked her magic on Henry, and he does whatever she asks. He evicts the queen from her throne and places her in exile. Then he declares that their marriage is null and void. He lavishes Anne with jewels and richly adorned fashions; gives male members of Anne's family grander titles, and promises to make Anne the queen of England. Anne bedazzles Henry because she raises his passions for her until he concedes to her everything she asks for. Finally they are married and Anne is crowned queen.

Anne becomes pregnant, but the baby is female. The child is names Elizabeth. Unfortunately, Anne is unable to give the king a son. In her attempts to do so, she miscarries, which is kept secret from the court and the king for fear that King Henry will also declare this, his second marriage, null and void. Anne becomes pregnant a third time. There are hints that Anne may have coupled with her brother to provide this pregnancy because Anne fears that the king had become impotent. This pregnancy also ends in miscarriage. The fetus is badly disfigured, and rumors fly about the court that Anne had made a pact with the devil through witchcraft in order to conceive a son.

During Anne's pregnancies, the king has been flirting with Jane Seymour, a young woman from the rival family. Anne finds herself in the same position as Henry's first wife—a deposed queen, at least in practice. In order to assure her complete departure, Anne is eventually tried as an adulteress, is found guilty, and is beheaded.

Throughout Anne's ordeals, Mary had returned to her husband, who dies shortly afterward from a disease referred to as the sweats. However, Mary later is courted by and falls in love with William Stafford, a man without title. By the end of the novel, Mary and William have married and conceived a daughter whom they name Anne. After Anne Boleyn is beheaded, Mary and William leave the court and retire to a small farm in the country with their children, Anne, Catherine, and Henry.