If you enjoyed PHM, you might also like: - For a more horror take, "There's no Antimemetic Division" https://qntm.org/scp. Without spoiling, it's about people trying to fight against a threat that's impossible to remember about. - Ted Chiang's "Understand". Again without spoiling too much, it's about a man whose intelligence rapidly increased. - Harry Potter and Methods of Rationality. Yeah, I'm serious, if you like the "smart character solves problem by thinking" it's amazing.