Must a novel about oppression be oppressive?

The suffering is relentless in Adam Johnson's novel "The Orphan Master's Son," and though I am really impressed by Johnson's writing and by his ability to incorporate research in a narrative, to tranform documentary material into a work of the imagination, the novel is very tough going and ultimately I can't really go with it all the way to the end. I'm sorry. I know the message is very powerful and contemporary - it's shocking to read about the tyranny and literally slavery that an entire national population must endure, right here in the 21st century, and every more shocking and disturbing to think how this country of almost primitive brutality exists as the northern half of a partitioned land and the neighboring country manufactures Hyundais by the billion. I know - freedom and capitalism are not one and the same, but can there be anyone on the planet sympathetic to the dynastic dictatorship of Kim Song Il or whatever the son's name is? That said, how much do we have to read about this occupied and oppressed land to get the point - by the 300th page of torture, terror, imprisonment, thought control, sycophancy to the Beloved Leader - I guess I've had it. As noted in previous posts, there's a whole genre of this kind of novel, not only the Soviet prison camp novels but you could add as a variant the Holocaust novels (Primo Levi, Elie Wiesel), the surrreal novels (Kafka) all variations on the theme of mind-deadening thought control enforced by brutality and terror - I admire Johnson for taking this on, for his courage and perspicacity, but in the end, or actually somewhat before the end, the novel became one relentless drumbeat, the theme pounded into us again and again, and I had to escape and I did.