Fifty years ago, at the 100th anniversary of Charles Baudelaire’s 1857 poetry collection “Les Fleurs du Mal” (Flowers of Evil), the French writer Pierre Jean Jouve stated, “‘Les Fleurs du Mal’ is no centenarian!” In 2007, on its 150th birthday, the book retains its freshness. A new prose translation by avant-garde American author Keith Waldrop (Wesleyan University Press, 228 pages, $24.95) and “The Writer of Modern Life: Essays on Charles Baudelaire” by Walter Benjamin (Harvard University Press, 320 pages, $15.95) are among the tributes suggesting that Baudelaire’s book is still path-breakingly modern.

Baudelaire (1821–1867) was obsessed with modernity and found inspiration in what he called the “ephemeral, the fleeting, the contingent.” He also embraced forbidden knowledge considered satanic by some stodgy 19th-century readers. If experience — of drugs, sexual immorality, or other debauchery — was morbidly evil, then the poet was determined to weave highly structured artificial flowers of immense power from such degradation. Typically uncompromising, the poet addresses us at the start of the book: “Hypocrite lecteur! Mon semblable, mon frère!” (Hypocritical reader, my ally, my brother).

Baudelaire’s life was grim, highlighted by unrequited love, penury, lack of critical acceptance, prosecution on charges of obscenity, and illness leading to his early death at 46 from syphilis. Some American fans have tried to add humor to alleviate the gloom, like the San Francisco writer Daniel Handler who in his mock-ghastly Lemony Snicket series of books for young readers dubbed his protagonists the “Baudelaire Orphans.” “Say it with Flowers” Baudelaire T-Shirts and tote-bags are sold online (cafepress.com) by Leaping Dog Press, a small literary publisher in Raleigh, North Carolina, and Baudelaire Soaps, a Swanzey, New Hampshire-based company (baudelairesoaps.com) explains that its bath and beauty products are named in honor of the poet, “or ‘Chuck’ as we call him around here.”

Ludicrous salutes distort our view of “Chuck,” as do the weighty Marxist musings of the suicidal German-Jewish essayist and toy collector Walter Benjamin (1892-1940), a talented writer whose reading of “Fleurs du Mal” as sociological evidence of 19th century Paris is narrow and eccentric, however fascinating. Marcel Proust and Théophile Gautier, to name only two, are more cogent guides to the writer. Proust’s critical text “Against Saint-Beuve” relishes Baudelaire’s “solemn diction” and “biblical idiom.” Gautier’s 1868 short book about Baudelaire calls his late friend the “morbid lover of the Hottentot Venus,” and evokes their mutual taste for “dawamesk,” a Middle Eastern jam made of opium, hashish, honey, almonds, and spices, and served — according to Baudelaire’s “Artificial Paradises” — on sacramental bread for ideal blasphemy.

A more sober contemporary portrait of Baudelaire may be found in the opera “Doctor Atomic,” which made its premiere in San Francisco in 2005 and is scheduled for the Chicago Lyric Opera this December and New York’s Met in 2008. The opera features physicist J. Robert Oppenheimer, the head of the Manhattan Project, who ranked “Les Fleurs du Mal” as the most influential book in his life. In 1945, while waiting for the first A-bomb to be tested in 1945 near Los Alamos, New Mexico, Oppenheimer sat reading Baudelaire. In their opera, the composer John Adams and librettist Peter Sellars have Oppenheimer sing Baudelaire’s lyrics and prose poems as an embodiment of a modern man who embraced knowledge, while realizing that it might be evil.

In his award-winning and still matchless 1982 verse translation of “Les Fleurs du Mal,” the American poet Richard Howard confesses that he “could not always love” the original poems, some of which are notably gruesome, describing hanged men and hideous old women in unflinching detail. Yet Mr. Howard adds, “Baudelaire’s poetry concerns us much more, and much more valuably, by its strangeness than by its familiarity.” Howard’s essay, reprinted in his “Paper Trail: Selected Prose 1965–2003” accompanies his sensitive renderings of mighty poems like “The Swan” and “The Albatross,” in which birds represent agonized emotional destines of exiles and poets. The majestically poignant “Invitation to the Voyage” has hypnotically seductive lines conjuring up an ideal elopement: “Mon enfant, ma soeur, / Songe à la douceur / D’aller là-bas vivre ensemble!” (My daughter, my sister, think how sweet it would be to go over there and live together!)

In past years, some American readers misread Baudelaire as a druggie, due to his poems and “Artificial Paradises,” a prose study describing his dabbling in hashish, opium, and other intoxicants. Yet Baudelaire was a diligent professional writer who produced a quantity of useful essays on art, literature, and music, as well as five volumes of still treasured translations of Edgar Allan Poe into French. Baudelaire reminded young writers, “Orgy is not the sister of inspiration; inspiration is absolutely the sister of daily effort.” The workmanlike side of Baudelaire was overlooked by party-going Beat writers like Allen Ginsberg and Jack Kerouac. Likewise, ennui as described by Baudelaire is not just idle boredom, as some lazier literati would have it, but spiritual lassitude and languor brought on by the struggle against an uncomprehending world.

Despite these and other misprisions, Baudelaire’s sheer power of language will ensure that “Les Fleurs du Mal” remains fresh and blooming as long as it has a single “Hypocrite lecteur.”

Mr. Ivry is author of biographies of Ravel, Poulenc, and Rimbaud, and the poetry collection “Paradise for the Portuguese Queen.”