Finished this novel and it's amazing and almost impossible to describe in a way that does it justice.
It's a science fiction novel, in the near-future sense where there's just a couple of things different. And it's also an alternate history book, but barely; it's basically a secret history novel built around a conspiracy theory. And it has one of my favorite tropes, the book-within-a-book. Oh, and it'a a legitimately interesting and useful history of modern Korea.
The concept: The Korean Provisional Government, which in our world ended in 1945 when Japan surrendered, actually never went away and still exists today in spite of the existence of North and South Korea. And the book-within-the-book reveals the entire secret history, told through a combination of legitimate facts about various figures like Syngman Rhee and Kim Il Sung, but also tons of events major and minor (I'd never heard of the assassination of Durham Stevens for instance). But it also meshes it stories from movies (including both Inchon and, I kid you not, Friday the 13th), and then there's entire narrative around the man reading the book and the Google/Meta-esque company he works for.
It's utterly weird and strange, but also compelling and a fantastic read.
Goodreads link if folks want more info and other people's opinions.