The book that launched modern poetry. Baudelaire found beauty in ugliness, sanctity in depravity, the sacred in the city's sordid streets. His "correspondances" (the idea that all the senses speak to each other and point toward a hidden unity) gave Symbolism its program. His treatment of spleen, ennui, and the erotic as serious poetic subjects opened the door for Rimbaud, Verlaine, and everything that followed.

The case for it, the case against, and the rest of the canon open with Pro.