The Strange Case of Dr. Jekyll and Mr. Hyde. by Robert-Louis Stevenson

The Strange Case of Dr. Jekyll and Mr. Hyde is the classic novella of split personality. Stevenson wrote it in just a few days while sick and bedridden, and famously burned the first draft after his wife suggested it should be written as an allegory and not as a story. He re-wrote it in three to six days, and after a few weeks of editing and revision he published what would become one of his most famous and best-selling works.
The story follows a London lawyer as he investigates the relationship between a brilliant scientist and a misshapen misanthrope. As the link between the two becomes clearer, Jekyll and Hyde develops into an allegory on the nature of good and evil.