I just read Denis Jackson's nice translation of Theodor Storm's Der Schimmelreiter (first published in 1888). For more about Storm, I recommend Jackson's great site about the author.
Storm’s novella contrasts two ways of responding to nature: there are the fanciful legends and superstitions of the community, and there is the more modern scientific and technological deployment of reason exemplified by the protagonist, Hauke Haien.
The story of Hauke’s life is told to a traveler by an old teacher, a ‘rationalist’ who doubts the supernatural elements of the tale. The teacher depicts Hauke as a great innovator whose engineering prowess gave him superior powers over nature, enabling him to design a better dyke to protect the community. The people repay Hauke with dark suspicion and rumors of his diabolical affiliation.
In the teacher's retelling of the story, the supposedly supernatural elements appear only ambiguously. So, e.g., there is a seemingly spectral horse, which is sold to Hauke by someone who laughs like ‘the devil’ (p. 72). But nothing much comes of this – the horse functions in the rest of the story like a natural though somewhat wild horse, one that only Hauke can tame (just as Hauke alone can tame the wild sea with better dykes). Then there's Trin Jans, who is presented not as a real witch but rather as ... well, as the sort of character who's a witch in more fanciful legends. There's also the suggestion that Hauke is cursed because he killed her cat (the cat came back, as it were). Thus, while the old teacher is aware of the supernatural aspects of the tale, he reigns them in to make them fit into a naturalistic interpretation.
The resulting narrative is in places quite eerie. Examples include the narrator's partly anthropomorphic characterization of some birds on the tidal flats (pgs. 22 & 99) and Trin Jans' uncanny story about a mermaid, which actually makes the mermaid seem terrifying, like something more and less than human (p. 98). In both cases the author embeds fragmentary human traits in what are ultimately strange, alien creatures that, like nature itself, efface humanity with a chilly indifference.
More generally, the tale charts a mundane landscape suffused with potentially supernatural elements that appear fleetingly in ambiguous forms, never quite surfacing as truly supernatural phenomena but, instead, appearing to be at home in the confines of nature. There is thus an ongoing juxtaposition of the world as (on the one hand) a natural order that fits the technical-scientific templates of reason and (on the other hand) a chaotic abyss from which wild, non-rational forces periodically erupt with cataclysmic effect.
These unpredictable natural forces find their echo within the human psyche. Hauke Haien, a paragon of reason, isn't alert to these destructive elements in his own soul, and so he's unaware of how they have eroded his own foundations over the years. Eventually, they catch him totally unawares, welling up from within and casting him into the abyss. Such a psychological reading is pursued in a meticulously Freudian direction by Anette Schwarz in her paper, “Social Subjects and Tragic Legacies: The Uncanny in Theodor Storm's Der Schimmelreiter” (The Germanic Review 73.3 [Summer 1998]: 251). Schwarz points out that neither Hauke nor his wife (Elke) has a mother who figures in the narrative (even though their fathers both loom large), and that Trin Jans stands in symbolically as the mother figure.
The most Freudian thing about Storm's novella, in my opinion, is its uncanniness. In describing the uncanny, Freud said that it characterizes fictional works that seem "to move in the world of common reality" but into which some strange, improbable or impossible events intrude. Freud focused on E. T. A. Hoffmann, but Storm's work seems a better epitome of Freud's theory.
Thomas Mann characterized Storm's achievement as "an art kind to the mystical and uncanny, the pagan northern art of [Der Schimmelreiter]. ... [I]t is precisely here ... that something of primeval power is finally achieved, some combination of human tragedy with the wild mystery of nature, something dark and heavy with the greatness and unknownness of the sea...." (Thomas Mann, 'Theodor Storm', 1930)
Update (Dec. 15, 2008): New York Review Books will re-issue James Wright's 1964 translation of this novella in early 2009. In their announcement of this upcoming publication, they quote from Kirkus Reviews the claim, "There is nothing better in German fiction prior to the work of Thomas Mann."