This is an odd one: it's a story of a romance with virtually no context. Sure, we get some idea of what Europe was like for a son of a wealthy family in the early 19th century. And, in one of the later chapters, Constant describes the physical geography of an area of Poland. But, beyond that, there's only Adolphe's emotions and his perceptions of Eleanor's. I don't know that I've read anything like it.
And though I don't know that I enjoyed it - I feel like the main characters' behaviour would only ever make sense in the Europe of the 18th, 19th and early 20th centuries - but it's remarkable how insular it is while managing to make you feel for them. And I think it must have had a major impact on later "psychological" novels, and I feel like Dostoevsky must have been familiar with it.