
At age 24, Flaubert saw Bruegel's painting,
The Temptation of Saint Anthony, and decided he would turn it into a play. Like all his literary projects, he took it very seriously. He wanted to describe a 3rd century hermit sitting on a mountain-top in the Egyptian desert and being tempted by the Devil, and he spent most of the rest of his life writing and rewriting it; the final version came out nearly 30 years later, only a few years before his death.
The rest of this review is in my book What Pooh Might Have Said to Dante and Other Futile Speculations