When a degree in English literature was finally floated at Oxford University in the late 19th century, there was no shortage of historians, classicists and other robust types to protest about so girly an option. It was Edward Augustus Freeman, the Regius Professor of Modern History, who uttered the famous killing phrase during a testy debate in Congregation: the new school, he said, lacked all rigour and objectivity and threatened to degenerate into ‘mere chatter about Shelley’. His quip has lasted rather better than his voluminous works about the Norman Conquest – usually in the improved version, ‘chatter about Harriet’. And generally, it must be said, people have agreed with Freeman, be they strenuously scholarly or exquisitely aesthetic. ‘Give us their poetry,’ the essayist Andrew Lang once imagined a reader protesting, ‘and leave their characters alone: we do not want tattle about Claire and chatter about Harriet; we want to be happy with “The Skylark” or “The Cloud”.’ Still, as Lang went on to reflect, if indeed ‘a man’s genius must be builded on the foundations of his character’, then the life of writers is not so obviously ‘chatter’ after all; and while a modern biographer wouldn’t put it in quite those terms, seeing what an author did with what life dealt him evidently remains something of interest both deep and wide.

The Harriet in question is the luckless first wife of Percy Bysshe Shelley and the mother of two of his children. Abandoned by the poet in favour of Mary Wollstonecraft Godwin, she ended up drowning herself in the Serpentine: she was 21 and pregnant, possibly with Shelley’s third child. A suicide note read, ‘My dear Bysshe, I could never refuse you and if you had never left me I might have lived.’ Harriet’s story is dreadful and pitiable. You can see why people find chattering about it so irresistible; and she was only one of a long string of casualties in these parts. Mary, whom Shelley married shortly after Harriet’s death, led a life of increasing desolation until left a widow at 25, and that was a positive primrose path compared to the experience of her half-sister, Claire, who made the big mistake of pitching the woo at Byron. Convinced their fates were intertwined, she wrote offering herself as one who ‘with a beating heart … should confess the love she has borne you many years’. Byron wrote to his own half-sister half-apologetically: ‘what could I do? – A foolish girl – in spite of all I could say or do – would come after me – or rather went before me.’ Claire bore him a daughter whom Byron insisted on having with him until, after mostly neglecting her, he sent her off at the age of four to be educated in a convent, where before long she was dead. It was the realisation of all Claire’s blackest nightmares: ‘Women could not live without making scenes,’ was reportedly Byron’s response when Shelley attempted to convey her distress.

More biographers must have tackled this extraordinary cluster of brilliant and doomed individuals than any other literary generation. It is striking that the bad behaviour of great writers should strike us with quite such force: perhaps it is because the assumption still runs so deep, despite the obvious evidence, that creative genius and moral intelligence somehow go together. ‘If men will impartially, and not asquint, look toward the offices and function of a poet,’ Ben Jonson once put it, ‘they will easily conclude to themselves the impossibility of any man’s being the good poet, without first being a good man.’ But then Jonson himself led a high old life – and Coleridge’s amendment is a nice one: ‘a good man, though not perhaps a goody man’.

Andrew McConnell Stott has here produced a very good account in which no one is a goody. He writes with wit as well as a deep acquaintance with the material, and he brings an enlivening novelistic feel to his pages without being trashy or cartoonish. He is agreeably sharp with his cast: Godwin appears at one point as ‘the bald, constipated narcoleptic that middle age had made him’ and Shelley as a creature with ‘large bulging eyes, long, wild, unmanaged curls and a high-pitched voice that would rise to an avian screech when he became agitated’. Stott is keen to evoke a disjunct no less bizarre between the liberationist rhetoric that often energised the circle and the sorry gender politics that seem largely to have dictated what actually went on. ‘What a set! what a world!’ Matthew Arnold was prompted to exclaim after reading Dowden’s life of Shelley in 1886. But Stott also manages to evoke how simply awful it must have been, in different ways, for everyone – even Byron, who, doomed to inhabit the myth of himself, would be gazed at wonderingly, a freakish magnificence, as soon as he entered a room. Lady Liddell, panicking, yelled to her daughter, ‘Don’t look at him, he is dangerous to look at.’

The chief originality of the book comes from Stott’s decision, among all the victims, to focus on Byron’s hanger-on and physician John Polidori. He was depressive, ambitious, not especially talented and chippy. Byron’s dislike for him is as funny as his dislike for Claire is sad: he was, said his employer, ‘exactly the kind of person to whom, if he fell overboard, one would hold out a straw, to know if the adage be true that drowning men catch at straws’. After his marginal life among the literary avant-garde Polidori returned to London, where, aged 25, in despair at his failure to make it, he finished himself off with prussic acid. ‘He had entertained too sanguine hopes of literary fame,’ Byron remarked sagely upon hearing the news.

But in fact his fame, of a limited kind, is secure as the author of The Vampyre, a creakily sensationalised portrait of his former master – ‘Who could resist his power?’ and so on – which, by a rough irony, he would live to see printed as a work from Byron’s own hand. (Thanks to the vagaries of copyright law, that meant he could not expect to earn a penny from his tale, so the hurt was more than emotional.) Polidori’s book helps Stott towards his slightly sensational title, along with the miserable cry of Harriet when Shelley disappeared: ‘The man I once loved is dead. This is a vampire.’ But in truth none of the actors here has much dedicated bloodthirsty cunning: it is a sequence of human ineptitudes, some well meant and more motivated by misplaced principle than by cruelty. What a set indeed. Arnold was not wrong; but they were very young.