If we had to recommend one single book of fiction, this would be the one. Unless there's an illustrated version that exists that we don't know about. We choose the Penguin edition because of the superior translation and reputable quality of Penguin books.
Là-Bas, translated as Down There or The Damned, is a novel by the French writer Joris-Karl Huysmans, first published in 1891. It is Huysmans' most famous work after À rebours. Là-Bas deals with the subject of Satanism in contemporary France, and the novel stirred a certain amount of controversy on its first appearance.
The plot of Là-Bas concerns the novelist Durtal, who is disgusted by the emptiness and vulgarity of the modern world. He seeks relief by turning to the study of the Middle Ages and begins to research the life of the notorious 15th-century child-murderer Gilles de Rais. Through his contacts in Paris, Durtal finds out that Satanism is not simply a thing of the past but alive in turn of the century France. He embarks on an investigation of the occult underworld with the help of his lover Madame Chantelouve. The novel culminates with a description of a black mass."