This story of a doctor who splits off his dark side with a potion might have been much more impressive in its psychology of duality when published in 1886. The novella kept me reading from start to finish, without really moving me--the story is kept at one remove until it's last few chapters by being seen through the perspective of Utterson, Dr Jekyll's friend and lawyer, a rather bland figure. The last two chapters are letters from a friend and colleague of Jekyll, then finally Jekyll himself, but it feels like an abrupt end because we never get Utterson's reaction to the revelations in those letters. A novel that did actually impress was a modern retelling, Mary Reilly by Valerie Martin, telling the story from the perspective of Jekyll's maid, who is unnamed and only briefly mentioned in the original.
