Carolus Rex Series by Andre Norton, Rosemary Edghill

Thrust into a volatile world where King Henry IX rules over the English Empire, America never revolted, and Napoleon Bonaparte marches unchecked across Europe, is young Sarah Cunningham, ripped from our history by magic and the machinations of the dying Duchess of Roxbury.Magically coerced into believing she is Roxbury, Sarah finds herself caught up with the Duke of Wessex, the King's most trusted spy... moreThrust into a volatile world where King Henry IX rules over the English Empire, America never revolted, and Napoleon Bonaparte marches unchecked across Europe, is young Sarah Cunningham, ripped from our history by magic and the machinations of the dying Duchess of Roxbury.Magically coerced into believing she is Roxbury, Sarah finds herself caught up with the Duke of Wessex, the King's most trusted spy. A perilous adventure takes them into the black heart of Imperial France to rescue a missing princess before the last chance for peace dissolves and the world is left at the mercy of Napoleon.... less

Under King Charles II, England's New World colonies are flourishing, as is France's colony Louisianne. Napolean is the dreaded Master of the European continent . . . And Sarah Cunningham, a woman from our own world, knows all too well what a difference this makes, for not long ago she was ripped from her life as a United States citizen in our history. Sarah, now the Duchess of Wessex, journeys to North America with her new husband, the Duke--but this is no pleasure trip... moreUnder King Charles II, England's New World colonies are flourishing, as is France's colony Louisianne. Napolean is the dreaded Master of the European continent . . . And Sarah Cunningham, a woman from our own world, knows all too well what a difference this makes, for not long ago she was ripped from her life as a United States citizen in our history. Sarah, now the Duchess of Wessex, journeys to North America with her new husband, the Duke--but this is no pleasure trip. The fate of the world--New and Old--rests on her saving her friend Meriel, rescuing Louis, rightful King of France, from the clutches of the Marquis de Sade, and finding the Holy Grail. But she and her beloved Duke are beset by perils that will test their strength and spirit to the utmost. less