Alison Weir takes an unromantic look at Anne Boleyn's last days in The Lady in the Tower. Starting with Anne's final miscarriage (she had three miscarriages or stillbirths after giving birth to Elizabeth, and Weir mentions the possibility that those losses were caused by Rh incompatibility), Weir traces the political machinations that led to Anne's death. By 1536, Henry, always mercurial, was becoming desperate for a male heir, and his courtiers knew it. Seeing that he was tiring of Anne's strong personality (which had originally attracted him), the Catholic factions put forward her opposite - sweet, compliant Jane Seymour.
But how to get rid of Anne? Divorcing Catherine of Aragon (now recently deceased) had cost Henry politically, so that wasn't a viable option. Fortunately for Henry (and for the Catholic faction at court), Anne had not endeared herself to the people or to the court. The same strong personality that first attracted Henry left her with no political capital to spend when his desire for an heir surpassed his desire for her. Her enemies convinced Henry she was a danger, put her in the Tower guarded by women (including her sister-in-law) who already disliked her. From there, it was only a few quick rumors to charges of adultery (highly unlikely since she was pregnant or recovering from a birth, stillbirth, or miscarriage for most of her time as Queen) and death by an executioner summoned before her trial began.