Margaret Cavendish was one of the most original, loveable and eccentric of women writers. Pepys called her "mad, ridiculous, and conceited" but when she paid her famous visit to London in 1667 he ran all over town to see her. And many of her other contemporaries were no less fascinated. Posterity has continued to feel the attraction; to her many admirers she has always been "the incomparable Princess," and Lamb enthusiastically praised her as "the thrice noble, chase, and virtuous—but again somewhat fantastical, and original-brain'd, generous Margaret Newcastle."

This biography is the first full-length study entirely devoted to the Duchess of Newcastle. It shows Margaret's metamorphosis from an imaginative, bashful child into a romantic public figure, and how, after living at home among a family unusual in its loyalties, she served as lady-in-waiting to Queen Henrietta Maria during the Civil War and in exile married William Cavendish, the "Loyal" Duke of Newcastle, before emerging as the first woman writer of her times—"Margaret the First" as she wished to be known.

Her poetry, fiction, drama and natural philosophy, along with her many other writings, are treated as facets of her extraordinary personality delightful in itself and also valuable as an illustration of the spirit of the age. The illustrations are unusually good and include a fine unpublished portrait of the Duchess, a photo of her effigy in Westminster Abbey and reproductions of several of the ornate engraved title-pages of her works.