The English Opium-Eater, By Robert Morrison

I love his writing but he was a loathsome human being. And it's a tribute to Robert Morrison, author of this engaging new biography of Thomas De Quincey, that I'm no better disposed towards the odious little creep than before. Morrison's balancing act is finely managed, for he remains attuned to the struggles faced by his subject while never losing sight of the fact that De Quincey was arrogant, selfish, and difficult. The result is an honest portrait – perhaps the most honest so far painted – of the man described by Wordsworth as "one of the most worthless of mankind".

Morrison follows in a distinguished line. Grevel Lindop's impeccable 1981 biography offered the most accurate and readable narrative of the life up to that point. But much has happened in the last two decades.

Morrison benefits from the new 21-volume Collected Works of De Quincey, published in 2003 under Lindop's general editorship, which brought to light many unknown works. For this biography, Morrison's is able fresh material includes newly-discovered letters: the result is an updated life of a writer whose failings are recounted in lurid and compelling detail.

Morrison is admirably straightforward those failings. De Quincey's taste for prostitutes began while he was at school and continued unabated for years. Even as a husband and father he pursued his "studies of the working poor" (as he called them) on solitary walks through nocturnal London.

And what on earth was he doing, sleeping for two months on the grave of the deceased three-year-old Kate Wordsworth in Grasmere churchyard? Morrison is right to say that "there was clearly a sexual element" in De Quincey's feelings for the child, as suggested by his lament for her "dear body" and "dear lips".

Morrison has new light to shed also on De Quincey's better-known proclivities. At a time when he was consuming no less than 8,000 drops of laudanum a day, De Quincey was "diluting" them with as much alcohol as he could find. "He doses himself with opium and drinks like a fish," Wordsworth's sister-in-law observed. Scholars are sometimes reluctant to use the words "alcoholic" and "De Quincey" in the same sentence, and Morrison's discovery that his writer was consuming "a toxic blend of opium and alcohol" explains why kicking the habit was only a pipe-dream. To the end of his days, De Quincey functioned thanks to a cocktail of drugs and drink, which gave him chronic constipation.

Yet opium was always the "hero" of De Quincey's story: "Thou hast the keys to Paradise, O just, subtle, and mighty opium!", as he put it. It was the substance that triggered visionary excursions that enabled him to enjoy once more his quasi-erotic relationship with the prostitute Ann of Oxford Street, and to meet crocodiles, snakes and Malayan travellers. He believed that its medicinal benefits included immunisation against tuberculosis and the suppression of "nervous irritation", whatever that might be.

In unbuttoned moments he could be self-aware. "I'm a hedonist," he once admitted, "and if you must know why I take opium, that's the reason". It was one of the few honest things he ever said. Morrison's new findings make clear that his subject was one of the most self-indulgent, self-regarding, callous men of letters who ever existed.

Only those qualities could explain De Quincey's unprovoked hostility towards a mother who supported him, financially and emotionally; his childhood precocity, arrogance and general uppitiness, especially when dealing with adults; his decimation of Wordsworth's orchard; his chilling conceit that serial killers were really "solitary artists"; his love-hate relationship with the demented Scottish journalist John Wilson and no less sociopathic colleague William Blackwood; his casual disregard for his children's education; his public back-stabbing of former friends (most obviously Coleridge and the Wordsworths), and his apparent indifference to news of the death of his son, Horace.

Nothing illustrates his character better than his politics. Though not alone in detesting Napoleon or celebrating Waterloo, De Quincey's implacable opposition to Catholic Emancipation and support of those responsible for the Peterloo Massacre in 1819 put him well towards the reactionary end of the spectrum. Morrison puts a brave face on De Quincey's attacks on the anti-slavery campaigner Thomas Clarkson but finds it harder to excuse his racist condemnation of "our brutal friends the Chinese", and articles which blame the Indian Mutiny on "princes and rajahs", and describe the sepoys as "infatuated savages".

British colonial rule, De Quincey believed, was inherently just, regardless of cost, and the world would have to learn to live with it. De Quincey idealised the poor (especially if they were beautiful and female) but reviled the Chartists and Corn League activists on the grounds that they wanted "to put an end to our whole polity and civil existence". They deserved imprisonment, in other words.

Morrison is even-handed in his judgements, taking care to place De Quincey's views in their precise context, but provides little cause to question Wordsworth's remark: "He is quite mad with pride." Throughout the life, De Quincey often seems to be a hair or two short of outright insanity. Whether discussing the state of the world or recounting his opium dreams, it is hard not to question his credibility and sincerity. Morrison's account of De Quincey's grief at the death of Kate Wordsworth is thoughtful – but even he has to admit that De Quincey's letters "stylize" his emotions.

Morrison is as good on the nitty-gritty of De Quincey's world – the hazards of riding outside mail-coaches, and hardships of living rough on the streets of London – as he is on the touchiness of Wordsworth and unreliability of Coleridge. He is especially good on De Quincey's precarious finances.

De Quincey seems constantly to have been pursued by unsavoury debt-collectors and wrote a stream of begging letters to virtually anyone who could help fund his habit. In addition, Morrison provides a compelling survey of De Quincey's work as biographer, satirist, economist, political commentator, translator, linguist and classicist. I cannot think of a more evocative introduction to the life and times of this remarkable writer.

When all is said and done, it is for De Quincey's Confessions of an English Opium-Eater that Morrison's biography will attract readers. The Confessions is a masterpiece of self-regarding egotism, composed in a magical and mysterious argot that spoke eloquently to the likes of Jorge Luis Borges, William S Burroughs and Charles Baudelaire, and which retains the power to whisk us into the realm of dream and nightmare. Its camp, rococo preposterousness was what inspired Edgar Allan Poe to claim it was composed "by my pet baboon, Juniper, over a rummer of Hollands and water".

Duncan Wu's biography of William Hazlitt is published by Oxford

Poppies and poets: Thomas de Quincey

Born in Manchester in 1785, a precocious student who never took his Oxford degree, De Quincey idolised Wordsworth (left) and moved to the Lakes. He began to write professionally in London after his marriage, and in 1821 caused a lasting sensation with his drug memoir, 'Confessions of an English Opium-Eater'. Settling in Scotland, he wrote for journals and published his 'Reminiscences' of the Lake poets. His opium use began in 1804 and continued intermittently almost until his death in 1859.