"Der Schimmelreiter" by Theodor Storm is a Gothic fiction novella published in 1888. In a small town in Northern Frisia, Hauke Haien rises from farmer's son to dykemaster, determined to revolutionize the coastal defenses with his mathematical knowledge. But as he battles both the sea and superstitious villagers who whisper about his mysterious white horse, tragedy looms. A tale of ambition, innovation, and supernatural legend, Storm's final work explores one man's struggle against nature and fate in a community that fears change.
Wikipedia page about this book: en.wikipedia.org/wiki/The_Rider_on_the_White_Horse