I thought of this question and its moral implications while reading The Strange Case of Dr Jekyll and Mr Hyde. Dr. Jekyll believes that all humans are divided creatures, split between good and evil. He wishes that the human mind could be freed from the struggle to reconcile the two, and so he uses his medical knowledge of drugs and their side effects to make a compound that will divide the low from the high. He feels as if doing this will allow him to become two separate people, and even creates a name for his darker self. But he soon learns that he cannot be free from the crimes of Mr. Hyde, which were far darker than he predicted.
I liked this story a lot, and recommend it. It's good to read a well-known classic and see how it was originally presented, free from the various adaptations. I like that, while it is essentially a horror story, it has an element of science fiction, with Jekyll's reference to experimenting with drugs that have known side effects. I was delighted that it is not revealed that Jekyll and Hyde are the same person until you are well into the novel, which seems to me an especially Victorian element. It's smartly written with an effort towards timelessness - Hyde goes out at night and does evil things. We don't know what - it is left to us to imagine what he does, to adjust his crimes to our own sense of evil.
According to some reading I've done on the novel's meaning, the Victorian interpretation was that good and evil exist in everyone, and attempts to repress your darker nature will cause it to erupt, and will cause great outbursts of evil. In my own reading of the novel, I perceive that Jekyll was more evil than he admits before dividing his soul. He wished that he could live without the struggle between his evil nature and Victorian morality, and his desire to free his evil side is the goal, not an effort to create a personality of pure goodness. At his transformation, he delights in the feeling of losing the reservations of morality. Only in fear for his life does he regret what he has done. The true horror of the tale is that he is a man without remorse throughout.
Next up is Dune by Frank L. Herbert. It comes highly recommended by a few fans of the novel. It is also difficult to find at the library; the library search engine is not designed to provide simple results for a simple search. When you type in "Dune", it pulls up an entire page of various novels in the Dune series, putting them in no logical order, so that you have to move on to the second page of results just to locate the first novel in the series. And of course, then you have to keep searching to find copies that are available at your local library. I think the catalog divides them between distinct editions of books, because a search for one novel may turn up several different results which are all the same novel, along with a few books about Dune, a book on dune buggies, and a children's book about deserts.
This is not meant as a complaint on my local libraries, which are excellent. I just wish some local benevolent tech genius would donate a new search engine to the library.