The seventy-eighth book: #67 Elective Affinities - Johann Wolfgang von Goethe
Known for his drama, I wasn't expecting Elective Affinities to be what Goethe wrote. The thesis, about how chemical elements have preferences in what they combine with, extends to a love sotry where a husband and wife have two friends live with them for a while, and how it changes the relationships and how they interact. The couple end up splitting up and get involved with their friends, as they turn out to be their better partners.
This is foreshadowed early in the book, as part of a scientific discussion, but comes back as the plot of the novel - something that makes there be a point to the story, and an exploration of the concept. It does create a 19th century romance novel after that, that doesn't necessarily always kept my interest (with a translation that didn't feel the most engaging), but works well to get to the point - it's a good novel, but I felt a bit out of touch with its setting.