This is the story of Shelley, Keats and Byron, their relatives and friends. It starts with the great Mary Wollstonecraft (1759-1797), notorious for writing an essay claiming that men and women are equal. Her first daughter, Fanny, could not find a respectable place in life and committed suicide. Wollstonecraft later married the philosopher Godwin, but died in childbirth giving birth to a second daughter, Mary, who at age 16 ran off to Europe with the poet Shelley, who was already married to Harriet, who later committed suicide. Godwin remarried and had another daughter, Claire. She became part of the Percy Shelley/Mary Godwin ménage, formed a romantic attachment with her brother-in-law, Shelley, possibly sexual, but unable to replace her half-sister in Shelley's affections, threw herself at the poet Byron, who was very rich and abnormally handsome. Byron accepted the offer of sex from the 18 year old Claire ("What would you do?"), and agreed to raise the resulting daughter, but then left his daughter to die of typhus in a Rome orphanage. He grew to detest Claire, who suffered greatly for her affair with Byron, and later in life vehemently renounced the "free love" which Wollstonecraft and Godwin had stood for.
There is more--the story of the journalist Leigh Hunt and the two years he spent in prison (he could not go out, but he could live in an apartment with his family, plenty of books and a piano), the story of Keats, who died young of tuberculosis in Rome, the story of Shelley's drowning off the coast of Italy and how it affected the other characters--but you can read it yourself. It is a long book, and every page is entertaining.
Aside from the stories of these people, the author wants to make the point that the "Romantic" poets were not at all isolated geniuses, as they were later portrayed. They formed cliques and coteries, entertained, loved and hated each other, walked in the woods together, played sports together, discussed poetry and philosophy together, and challenged each other to experiment with various modes of writing. These interactions gave rise to their great works.
The author of this book, being a woman, has insights a man might miss ("Shelley was out all day .... with the ever-faithful Claire at his side, and [pregnant] Mary had little to do except sit at home reading, and feel fat and unwanted."), and a refined sense of social relations.
You also learn a lot about how life was for people in the early 1800s. Women often died in childbirth, so there were a lot of half-brothers and sisters around, and in some cases, like with Byron and his half-sister, they fell in love and had sex. Also, many children died in childbirth. Women were always worn down by pregnancy, and always losing children. It never seems to have occurred to their husbands to withdraw before ejaculation, or to have non-penetrative sex.
But women could be obtuse as well. Both Mary and her sister Claire fell in love and had children by married men, despite the dangers, both physical and social. A woman who could not form a respectable marriage was condemned to become a hanger-on in a relative's household. That led to other complications, because the only available men were their sisters' husbands. Or, if they could not find a place in a relative's household they could try to become a governess in a stranger's household. Of course the only men available there would be their employers. No wonder so many women committed suicide. Mary Shelley wrote Frankenstein.
All the while, everyone devoted much of their lives to writing letters and diaries, which is why we know so much about them. I suspect scholars will quibble with some of the interpretations of the evidence, but I for one am very happy this book was written, for many reasons, not least that it got me reading Shelley, Keats and Byron again.