Thomas De Quincey (1785-1859) stands, with William Hazlitt and Charles Lamb, among the best essayists of the romantic era. Aside from a Gothicky novel called "Klosterheim," virtually everything De Quincey wrote was relatively short, though his range was exceptionally broad: conservative political tracts, tales of terror (the best is "The Avenger"), articles about classical literature and assorted literary reminiscences, chiefly of the poets Wordsworth and Coleridge. At the end of his life, his collected works spanned 14 volumes.

This is remarkable because, for most of his adult existence, De Quincey was an opium addict, an alcoholic in all but name, and a man who spent years dodging creditors, constantly moving from one rented room to another. What money he didn't spend on laudanum - his preferred opium-alcohol mixture - he spent on buying thousands of books, many of them pricey and rare. For years he rented Dove Cottage, Wordsworth's old home in the Lake District, and essentially used it to store his library and papers. Though from an upper-middle-class family and exceptionally well educated in Latin and Greek, De Quincey nonetheless dropped out of Oxford, eventually married his housekeeper (who bore him eight children) and was regularly shamed by public announcements of his nonpayment of bills. He contributed to multiple magazines, Blackwood's being the best known, and sooner or later quarreled with nearly all his editors. In person, he was diminutive (under five feet tall) and exceptionally courtly in his manner and speech.

Today De Quincey is remembered, and by some revered, for his evocative (at times purple) prose and for two or three of the most influential works of the 19th century, the most famous being the autobiographical "Confessions of an English Opium-Eater." No less an authority than William Burroughs has called "Confessions" "the first, and still the best, book about drug addiction. . . . No other author since has given such a completely analytical description of what it is like to be a junky from the first use to the effects of withdrawal."

In this lucid, deeply researched biography, Robert Morrison makes plain that De Quincey wasn't just a recreational user, but truly a slave to his habit. He would regularly pop pills - laudanum capsules that he kept in a snuffbox - even in the presence of company. Although De Quincey tried repeatedly to break the drug's hold over him, the consequent shakes, fevers and depressions would eventually destroy his resolve. And yet two sections of "Confessions" are honestly titled: "The Pleasures of Opium" and "The Pains of Opium," for the drug lifted some of life's burdens, even as it imposed others. It also allowed for vivid, hallucinatory dreams and memories, often of the dead: the beloved sister whom De Quincey lost when young, the prostitute Ann who shared his early miseries, the 3-year-old Wordsworth daughter he played with and adored, his own deceased children. In opium visions they might all, for a moment, live again.

Throughout his life De Quincey wrote repeatedly about himself in what one might call supplements to the "Confessions." These include "Suspiria de Profundis" ("Sighs From the Depths") and "The English Mail-Coach," which opens with a paean to speed, to the thrill of racing along pitch-black roads at night, and ominously titles one chapter "The Vision of Sudden Death." If, in some lights, De Quincey may be viewed as a proto-Burroughs, as well as a British cousin to Edgar Allan Poe and Charles Baudelaire, he might with a stretch even be seen as an ancestor of the J.G. Ballard who wrote "Crash."

As a practicing literary critic, De Quincey memorably distinguished between "The Literature of Knowledge and the Literature of Power," that is, between those works that add to our stock of learning, that teach, and those that move us and affect our souls. "The Literature of Knowledge" is inherently provisional and, like any science text or cookbook, open to additions and revision; not so the "Literature of Power." As De Quincey writes, "A good steam-engine is properly superseded by a better. But one lovely pastoral valley is not superseded by another, nor a statue of Praxiteles by a statue of Michael Angelo."

This hard-scrambling journalist's other permanent contribution to scholarship - an anthology favorite - is "On the Knocking at the Gate in Macbeth." Here De Quincey probes the "peculiar awfulness" and "a depth of solemnity" he had always felt when, after Macbeth and his wife have murdered the king, they suddenly hear the sound of knocking at the castle door. In De Quincey's view, the killing of Duncan occurs during a "suspension and pause in ordinary human concerns," in a kind of temporal "parenthesis," and the knocking signals the return to the normal goings-on of the world, while also revealing to the Macbeths the full horror of what they have just done.

Murder, in fact, always deeply fascinated De Quincey and comes to the fore in his wittiest essay, the savagely deadpan "On Murder Considered as One of the Fine Arts." Conceived as a lecture to a society of connoisseurs, it remains the foundational text for the grisly black humor of films such as "Kind Hearts and Coronets" or Patricia Highsmith's novels about the talented Mr. Ripley. As our lecturer observes: "Something more goes to the composition of a fine murder than two blockheads to kill and be killed, a knife, a purse, and a dark lane. Design, gentlemen, grouping, light and shade, poetry, sentiment, are now deemed indispensable to attempts of this nature."

Alas, the wholly aesthetic murder can be elusive: "Awkward disturbances will arise; people will not submit to have their throats cut quietly; they will run, they will kick, they will bite; and, whilst the portrait-painter often has to complain of too much torpor in his subject, the artist in our line is generally embarrassed by too much animation."

What's more, the practicing connoisseur requires firmness of character. Otherwise, "if once a man indulges himself in murder, very soon he comes to think little of robbing, and from robbing he comes next to drinking and Sabbath-breaking, and from that to incivility and procrastination. Once begin upon this downward path, you never know where you are to stop. Many a man dated his ruin from some murder or other that perhaps he thought little of at the time."

If you've never read Thomas De Quincey, you should first pick up a good selection of his writings. Afterwards, when fascinated by the man, as you will be, turn immediately to this excellent, detailed and often harrowing biography, "The English Opium-Eater."

Dirda reviews books every Thursday in The Post.

THE ENGLISH OPIUM-EATER

A Biography of Thomas De Quincey

By Robert Morrison.

Pegasus. 462 pp. $35