The Temptation of St. Anthony by Gustave Flaubert
A work of singular genius. The plot is simple: Anthony, a monk, goes out to the desert to meditate, gets tempted. But what temptations! Flaubert pulls out all the stops in a decadent, phantasmagorical, hallucinatory, excessively brilliant novel. While the book is written like a play, it is clearly a novel, since staging this would be impossible. (Maybe Terry Gilliam or Michel Gondry could film it?)
Our benighted monk gets tempted by all manner of beasts, demons, and sexy ladies, while the reader is treated to a panoply of cults, heresies, and sects, fighting for his attention.
While a literary curiosity at the time, the book went on to influence James Joyce. The “Nighttown” section of Ulysses (corresponding with Circe, shape-changing, and Walpurgisnacht) bears Flaubert’s influence.