Though he is an awkward figure, afflicted by romantic sensibilities about love, not particularly adept at anything practical, and subject to rapidly changing moods, Friedrich remains someone we can sympathise with, clinging to rationality and gentle despite the violence of his obsession. And Sibylle, worldly and promiscuous but at the same time child-like, is a surprisingly sympathetic femme fatale, so there is no jar when the narrative switches to her perspective several times towards the end. (Her character is based on a real actress of the same name, and Friedrich's story has significant autobiographical elements.)
A Sad Affair (Eine unglückliche Liebe, 1934) begins with a boundary crossing and a passing vision of the flames of war and the lure of the high seas, but otherwise offers no hint of the political events of the early 1930s. Koeppen does, however, describe the more immediate setting to his intimate drama: the hotels and streets and night-life of the unnamed city that is clearly Zurich, the bohemian drama troupe Sibylle is working with, and so forth. The "decadence" here was enough to make A Sad Affair unpopular with the Nazis.
Koeppen's first novel is overshadowed by his three novels from the 1950s, dealing with the corruptions and compromises of post-war Germany, but the more personal A Sad Affair has a charm all of its own.