"If opium-eating be a sensual pleasure, and if I am bound to confess that I have indulged in it to an excess, not yet recorded of any other man, it is no less true, that I have struggled against this fascinating enthralment with a religious zeal, and have, at length, accomplished what I never yet heard attributed to any other man - have untwisted, almost to its final links the accursed chain which fettered me." (from Confessions of an English Opium Eater)
De Quincey's autobiographical account of his opium addiction is his most famous work. De Quincey took opium initially to ease physical pain but eventually increased the dosage enough to become addicted. He did hold to the belief that at the time he began using opium daily, he had no other choice.
The book gives eloquent descriptions of the psychological effects of the drug. The book sounds a lot like the novels of the period where the reason behind his actions seems more important than what he was actually doing, especially toward the end.
It was interesting to read this along with "Over the Underpass". While they were written almost two centuries apart, the story of drug abuse and how it can make a slave of anyone is still that same.