I'm not sure if some of the book's oddities - Lumi's extreme calm, Sol's unknowability, the emotionally distanced feeling in a story whose action is entirely driven by a marriage, the very open ending - are flaws or exactly what the author intended.

Tonally it sounds very similar to the other Itäranta I've read, The City of Woven Streets, so I'd go with "intent." It was a very dreamlike book.