Fact and fiction and how they play off one another in The Orphan Master's Son

I don't know how it will play out but the first 50 or so pages of Adam Johnson's novel "The Orphan Master's Son" are quite harrowing - describes young man's upbringing in a North Korean orphanage - far beyond the horrors of orphanages in the standard Victorian or Dickensian version - and then his induction into a military unit where his job - he's about 16 years old - is to take a small skiff to the Japanese coast and kidnap people who they can spy at dusk walking alone on the a beach of a pier. It's horrible and ruthless, though the young man Jung Do, does have sensibilities - yet of course he has no choice and no option but to go along or be killed. It's very tense and difficult to read this - and yet it does raise some questions: Is this entirely a work of the imagination or is it, as I've heard, based on sources? If it's based on sources, why isn't it a nonfiction account? If it is fiction, is it true to a North Korean experience and if so how true? Is our reaction to it, or my reaction, a response to the novel as a work of fiction or as a representation of life in a country today? Would the novel carry the same emotional weight if it were a clearly fictionalized country - or someplace in a future century?