If you like Philippa Gregory
A Royal Affair

Elizabeth: The Golden Age
By Tasha Alexander
The reign of Queen Elizabeth I was a time of war, passion, and spectacular achievement. Elizabeth faces an open challenge from the Spanish King Philip II, who is determined to restore England to Catholicism with his powerful army and dominating armada. Preparing to go to war to defend her empire, Elizabeth struggles to balance ancient royal duties with an unexpected vulnerability: her love for the seafarer Sir Walter Raleigh.

Duchess of Aquitaine: A Novel of Eleanor
By Margaret Ball

Beautiful and brilliant, Eleanor is the daughter of the duke of Aquitaine. Everyone knows that a girl of fifteen cannot possibly hold the richest dukedom in France. Everyone, that is, except for her dying father, who insists on leaving Eleanor his most valuable provinces. In order to safeguard her lands and her life, Eleanor devises a scheme to marry the heir to the throne of France. But she must learn to be careful what she wishes for. Eleanor’s husband is a cautious man, whose wit and courage do not always match Eleanor’s own; and she ultimately finds herself seeking an even greater match with Henry II of England.

The Dark Queen: A Novel
By Susan Carroll

When a wounded captain of the Navarre army arrives on Faire Isle in 1572 and calls for an audience with Daughter of the Earth (aka healer, or witch) Ariane Cheney, he provokes the wrath of the eponymous queen of France, Catherine de Medici.  Don’t miss the rest of the Dark Queen trilogy.
**Annotated from Publishers Weekly**

The Queen of Subtleties
By Suzannah Dunn

She was the dark-eyed commoner who captivated a king, causing a monumental upheaval in the land that would sever England from the rest of the Western world. Yet, after three short years of marriage, she would die by the headsman's sword, leaving behind a young daughter destined to rule as the greatest of all British monarchs. With stunning vividness, Dunn brings a tumultuous era to life, as she boldly reimagines the rise and descent of tragic, legendary queen Anne Boleyn, the second wife of King Henry VIII.
Also:  Sixth Wife: She Survived Henry VIII to be Betrayed by Love

A Rose for the Crown
By Anne Easter Smith
As Kate Haute moves from her peasant roots to the luxurious palaces of England, her path is inextricably intertwined with that of Richard, Duke of Gloucester, later King Richard III. Although they could never marry, their young passion grows into a love that sustains them through war, personal tragedy, and the dangerous heights of political triumph.
Also:  Daughter of York

The Hidden Diary of Marie Antoinette
By Carolly Erickson
Imagine that, on the night before she is to die under the blade of the guillotine, Marie Antoinette leaves behind in her prison cell a diary telling the story of her life—from her privileged childhood as Austrian Archduchess to her years as glamorous mistress of Versailles to the heartbreak of imprisonment and humiliation during the French Revolution. Erickson brilliantly captures the queen’s voice, her hopes and her suffering.
Also available: The Last Wife of Henry VIII, The Secret Life of Josephine: Napoleon's Bird of Paradise, The Tsarina's Daughter

A Lady Raised High
By Laurien Gardner
Young Anne Boleyn entranced the most powerful man of his time, King Henry VIII. But she would not yield to him unless he offered her marriage and the Crown. To win her, Henry would challenge the powers of Heaven--and create upheaval on Earth.
Also: Plain Jane

Mary Queen of Scotland and the Isles  
By Margaret George

By her eighteenth birthday, Mary was a widow who had lost one throne and had been named by the Pope for another. And her extraordinary adventure had only begun. Defying her powerful cousin Elizabeth I, Mary set sail in 1561 to take her place as the Catholic Queen of a newly Protestant Scotland. A virtual stranger in her volatile native land, Mary would be hailed as a saint, denounced as a whore, and ultimately accused of murdering her second husband in order to marry her lover. By twenty-five, she had fled Scotland for the imagined sanctuary of Elizabeth's England, where she would be embroiled in intrigue until she was beheaded like a criminal.

The Innocent: A Novel
By Posie Graeme-Evans
Deep in the forest of western England, a baby is born. Her name is Anne.  Fifteen years later, England emerges into a fragile but hopeful new age, with the charismatic young King Edward IV on the throne. Anne, now a young peasant girl, joins the household of a wealthy London merchant. Her unusual beauty provokes jealousy, lust, and intrigue, but Anne has a special quality that saves her: a vast knowledge of herbs and healing. News of her extraordinary gift spreads, and she is called upon to save the ailing queen. Soon after, Anne is moved into the palace, where she finds her destiny with the man who will become the greatest love of her life -- the king himself.
Also:  The Exiled, The Uncrowned Queen

Mistress of the Sun: A Novel
By Sandra Gulland

Based on the life of Louise de la Vallière, who, against all odds, became one of the most mysterious consorts of France's Louis XIV, the charismatic Sun King.  Unmarriageable, and too poor to join a convent, Louise enters the court of the Sun King, where the king is captivated by her. As their love unfolds, Louise bears Louis four children, is made a duchess, and reigns unrivaled as his official mistress until dangerous intrigue threatens her position at court and in Louis's heart.

Also, don’t miss her riveting trilogy featuring Josephine Bonaparte. 

The Secret Wife of King George IV
By Diane Haeger

Although it was illegal, secret, and against the express commands of his famously mad father, King George IV of England married twice -- once for duty and once for love. While Caroline of Brunswick eventually became his lawful queen, it was the beautiful Maria Fitzherbert, recognized as his wife by the Catholic Church but not by the laws of England, who claimed his heart.

Also:  Courtesan, The Ruby Ring, The Perfect Royal Mistress, The Secret Bride: In the Court of Henry VIII

The First Princess of Wales
By Karen Harper
It is the 14th century, the height of the Medieval Age, and at the court of King Edward III of England, chivalry is loudly praised while treachery runs rampant. When the lovely and high-spirited Joan of Kent is sent to this politically charged court, she is woefully unprepared. Joan plots to become involved with the prince to scandalize the royal family, for they engineered her father’s downfall and death. But what begins as a calculated strategy soon—to Joan’s surprise—grows into love. When Joan learns that Edward returns her feelings, she is soon fighting her own, for how can she love the man that ruined her family?
Also: The Last Boleyn

I, Victoria
By Cynthia Harrod-Eagles

A fatherless girl grows up a virtual prisoner in the shabby backwater of Kensington Palace, despised by her royal relations, bullied and insulted by her foolish mother's evil genius. Only the core of stubbornness in her character sustains her as she waits for the day of deliverance - the day she will become Queen of England. She is Victoria; this is her story, recorded in her own words during the last troubled year of her life.  

The Book of Eleanor: A Novel
By Pamela Kaufman
In 1137, fifteen-year-old Eleanor became Duchess of Aquitaine, a wealthy and powerful province in France. Rich and influential in her own right, her tumultuous marriages thrust Eleanor into the political and cultural spotlight. A lifelong rebel, Eleanor would defy her husband and the Church, and eventually strong-arm the Pope into annulling her marriage. Once free, Eleanor thought to marry her childhood love, but found herself forced into another political marriage, this time with a more dangerous husband—Henry II of England.

The Secret Diary of Anne Boleyn
by Robin Maxwell

Anne Boleyn was the second of Henry's six wives, doomed to be beloved, betrayed, and beheaded. When Henry fell madly in love with her, he was already married to Catherine of Aragon. But his passion for Anne was great enough to rock the foundations of England and of all Christendom. But all too soon his passion faded; when Anne bore him not the promised son but a daughter Henry forsook her for another love, schemed against her, and ultimately had her sentenced to death.

Also: The Queen's Bastard, Virgin, The Wild Irish, To the Tower Born, Mademoiselle Boleyn

I, Elizabeth
By Rosalind Miles

Last in the line of succession to the English throne, Elizabeth inherited a country torn by religious differences, at war with Europe, and badly in debt. When she died in 1603, having ruled for forty-five years, her empire was solvent, the Spanish Armada had been defeated, the Church of England had been firmly established, and the men she favored, such as Sir Francis Drake and Sir Walter Raleigh, had made her reign the Golden Age still remembered today. 

Abundance: A Novel of Marie Antoinette
By Sena Jeter Naslund

From the lush gardens of Versailles to the lights and gaiety of Paris, the verdant countryside of France, and finally the stark and terrifying isolation of a prison cell, the young Marie Antoinette’s life is joyful, poignant, and harrowing by turns. As her world of unprecedented royal splendor crumbles, the charming queen matures into a heroine of inspiring stature, one whose nobility arises not from the circumstance of her birth but from her courageous spirit.

Loyal in Love: Henrietta Maria, Wife of Charles I
By Jean Plaidy
The first in her Queens of England series, the daughter of Henry IV of France, Princess Henrietta Maria, becomes a political pawn when her father marries her to Charles I of England. Sent abroad, she finds herself living in a Protestant country that views her own faith—Catholicism—with deep suspicion.  Henrietta is passionate about her faith, however, and soon politically powerful people turn her loyalty to her religion into a focal point for civil war. Don’t miss any of Plaidy’s other rich historical novels!

The Winter Prince
By Cheryl Sawyer
Mary Villiers, Duchess of Richmond and Lennox, is a ravishing beauty raised as the adopted daughter of Charles I of England. In 1642 she is shocked to find herself opposed to her king when he decides to declare war on Parliament and therefore on his own people. Mary embarks on a dangerous quest to help save the throne of England for its rightful monarch, but first she'll tangle with the king's charismatic nephew, Prince Rupert of the Rhine.

Royal Harlot: A Novel of the Countess of Castlemaine & King Charles II
By Susan Holloway Scott
London, 1660: Ready to throw off a generation of Puritan rule, all England rejoices when Charles Stuart returns to reclaim the throne. Among those welcoming him is young Barbara Villiers Palmer, a breathtaking Royalist beauty whose sensuality and clever wit instantly captivate the handsome, jaded king. Though each is promised to another, Barbara soon becomes Charles's mistress and closest friend, and the uncrowned queen of his bawdy Restoration court.
Also: Duchess: A Novel of Sarah Churchill, The King's Favorite: A Novel of Nell Gwyn and King Charles II

Fatal Majesty: A Novel of Mary, Queen of Scots
By Reay Tannahill

Combining the romance and drama of Margaret George with the sophistication of Umberto Eco and Peter Ackroyd, "Fatal Majesty" focuses on Mary, Queen of Scots, the center of one of the most complex and violent political eras in the annals of British history.

Farewell, My Queen: A Novel
By Chantal Thomas

A woman whose function it once was to read books aloud to Marie-Antoinette is haunted by the memory of her last days at the French court of Versailles, when Louis XVI's magnificent chateau succumbed to the irrepressible forces of revolution. Now exiled in Vienna, Madame Agathe-Sidonie Laborde looks back twenty-one years to the legendary opulence of Versailles and discovers the full measure of her fascination with the Queen she served.

Innocent Traitor: A Novel of Lady Jane Grey
By Alison Weir

Lady Jane Grey–“the Nine Days’ Queen”– is a fifteen-year-old girl who unwittingly finds herself at the center of the religious and civil unrest that nearly toppled the fabled House of Tudor. Unabashedly honest and exceptionally intelligent, Jane possesses a sound strength of character beyond her years that equips her to weather the vicious storm. And though she has no ambitions to rule, preferring to immerse herself in books, she is forced to accept the crown, and by so doing sets off a firestorm of intrigue, betrayal, and tragedy.

Also: The Lady Elizabeth and many nonfiction royal biographies.