A novel of heroism without heros : Comedy in a Minor Key

Hans Keilson's "Comedy in a Minor Key" is a very strange book, and I won't be giving anything away if I tell you the plot because that's exactly what Keilson does: it's a very short novel (135 small pages) about a Dutuch couple harboring a Jewish man in their attic during WWII, under Nazi occupation; Keilson begins the novel at the end, as the opening scenes are during a British (?) air invasion, flying over Holland to a bombing mission, so liberation and the end of the war are in sight, but the habored Jew, Nico, is very ill, and after the flyover he dies - a doctor comes to certify the death and the doctor and the man of the house, Wim, make plans to bury Nico's body. Then we jump back to the arrival of Nico in the home, about a year before. Throughout, we jump back and forward in time, it's a novel in pieces (though not at all difficult to follow because the action, such as it is, is very simple and there are essentially only 3 characters and one setting), and the effect is something like a Cubist painting, with the full picture coming together gradually through broken images. I wonder why, however, a writer would give up the possibility of building narrative and dramatic tension, why he would completely flatten the arc of the story? Is it because the death of Nico would be such a let-down as the conclusion of a novel about sheltering a Jew during the war? Keilson is very ruthless and honest with his material - gives a real sense of the awkwardness as well as the danger of the situation, and makes clear that the couple are doing their "patriotic duty," but that they are also full of ambivalence - a novel of heroism without heroes.