When Mary Wroth's fiction reached print, an offended lord called its author a monster. She wrote him a poem too.

Mary was born Mary Sidney on 18 October, probably in 1587, into a family whose writing would help shape the literature of Elizabethan England. Her father, Robert Sidney, was a poet. Her uncle was Sir Philip Sidney, author of the Arcadia, a romance of princes, shepherds and complicated love. Philip had died in 1586, before she was born. His books remained, and so did his sister, another Mary Sidney, the Countess of Pembroke.

This Mary was the child's aunt and godmother. She wrote poetry, translated, helped bring her dead brother's work into print and completed the verse translations of the Psalms they had begun together. Her translations from the French were published in 1592. At Wilton, her household gathered writers and scholars. A girl in this family did not have to imagine what a woman with literary authority might look like. There was one already.

For much of Mary's childhood her father was governor of Flushing in the Netherlands, and she spent long stretches at Penshurst Place in Kent and at her aunt's London house, Baynard's Castle. News of the children crossed the sea to him by letter. In 1595 the family's agent reported that Mary was "very forward in her learning, writing, and other exercises she is put to, as dancing and the virginals." The children were kept at their books. They danced, they sang, they played the lute.

On 27 September 1604 she married Sir Robert Wroth, an Essex landowner. Elizabeth I was dead, James I was king, and Mary entered the new court. On Twelfth Night 1605 she danced at Whitehall in Ben Jonson's Masque of Blackness, alongside Queen Anne herself. Jonson later dedicated The Alchemist to her. She had inherited literary connections, and she was making connections of her own.

In February 1614 she gave birth to a son, James. On 14 March her husband died. The boy was a month old, and his mother was a widow with substantial debts entangled in the property his father had left.

James lived for another two years. He died in July 1616, and the estate passed to her husband's male heir, John Wroth. Mary had lost her child, and with him the claim on which her position depended. Her debts remained. The law could settle where the land went without settling what she was to live on.

During her widowhood she also bore two children, Katherine and William, to her first cousin William Herbert, Earl of Pembroke, the son of her literary aunt. He was a poet and patron, powerful at court and already married. Their relationship placed Mary's private life close to the subjects she was exploring in her work: desire, fidelity, the unequal bargain between the person who remains constant and the person who does not.

In her sonnet sequence, Pamphilia to Amphilanthus, the lover doing the speaking is a woman. She longs, doubts and examines her own attachment. The familiar arrangement of a male poet describing a beautiful woman has been turned around. Here the woman has the words, and the man is the uncertain beloved her thoughts keep returning to.

Mary gave that voice sustained attention. Between about 1615 and 1620 she copied the sequence out in her own hand, correcting as she went. In one sonnet her speaker says, "I am the soul that feels the greatest smart; I am that body lives deprived of heart." Mary struck through the last five words and wrote above them "heartless trunk of hearts depart". Even the language of helplessness was hers to revise.

The sequence appeared with The Countess of Montgomery's Urania in 1621, the first known original prose romance by an Englishwoman. It was an enormous book, carrying many lives and stories through an imagined world of courts and kingdoms, and at its centre was the constant Pamphilia's love for the inconstant Amphilanthus. Her uncle's Arcadia had been read for a generation. Now a Sidney woman had written a romance of her own.

Some readers looked through the invented names for people they knew.

Edward, Lord Denny, believed one story in Urania exposed a scandal in his own family. His answer was a poem that passed from hand to hand in copies, calling Mary a "hermaphrodite in show, in deed a monster". It closed with advice: "Work o' th' works, leave idle books alone, / For wise and worthier women have writ none." An objection to a fictional portrait had become an attack on any woman who wrote one.

Mary answered in verse, accusing him of lying and drunkenness, and borrowing his own rhymes to do it. Her poem closed: "Take this then now, let railing rhymes alone, / For wise and worthier men have written none." She had turned 'women' into 'men'.

In their letters in February 1622 he urged her towards religious writing, holding up the example of her learned aunt and her translations of the Psalms. The family had supplied Mary with a precedent for authorship. Denny supplied instructions about which parts of that precedent she ought to follow.

By then she had already written to the king's favourite, the Marquess of Buckingham, assuring him she had never meant her book to offend anyone and that she had stopped its sale. The printed Urania was halted. The work was not. She also wrote a continuation, preserved in manuscript, with additions and revisions in her own hand.

The continuation is now in the Newberry Library in Chicago. Across its pages Mary corrected and expanded the world she had made, as she had once corrected the words of her love poem. It stayed unpublished through her lifetime and for centuries afterwards. The first printed edition appeared in 1999, almost 380 years after a lord told her to leave idle books alone.