"Satan's Diary" (1919) by Leonid Andreyev is a dark, satirical novel in which Satan descends to Earth, taking human form, in order to study mankind. Expecting to find grandeur and power in human society, he instead encounters hypocrisy, greed, corruption, and cruelty. As he mingles with people of wealth, politics, and culture, Satan grows increasingly disgusted by their pettiness and moral decay. The novel critiques post-World War I society, exposing the collapse of values and the dominance of materialism. Through Satan's perspective, Andreyev delivers a bitter condemnation of humanity's weaknesses, showing that mankind's vices rival or even surpass the Devil's own.