Books about Genocide

I'm going to backtrack a little to Ung's "First They Killed My Father." It made me think of other books we've read about genocide, like "What is the What?" When comparing the two, I immediately recall Ung's skillful manipulation of description and specific details that I enjoyed. I think I'm able to remember Ung's story more clearly because it was paced expertly, keeping the reader captivated and involved. I was able to read the book in pretty much one sitting (on an airplane). When I think about "What is the What" I cannot even remember what the "what" was. I remember the joyous feeling I had when I managed to escape failure on a plot quiz. I remember feeling like the book was endless, especially when the protagonist was going through the desert. While the style of writing really made the reader FEEL like they were traveling through an endless desert, I constantly found myself tuning out. Like in "the Bookseller of Kabul," the author of "What is the What" didn't narrate historical explanations very well. I think the length of Ung's story intensified the pathos that the text evoked in me because I felt like the characters were being torn from the story. This was a pretty unorganized rant but my point: Ung's story about genocide was more effective than that of "what is the what."