Why we care about the characters in My Struggle

Can there be any more painful honesty than Karl Ove Knausgaard's My Struggle?, which in volume 2 goes into excruciating detail about the early years of his relationship with Linda - whom we know now to be his wife and mother of his 3 children - but as we see them in the first years of their relationship we think that they might kill each other, quite literally: they are both so troubled, KOK having a very serious alcohol problem and it's not clear that he even recognizes this in the present of 2009, when he's actually writing volume 2, and Linda with some type of psychological condition, probably bi-polar, and we know that she made a semi-serious attempt to kill herself by jumping from a window. At first, as is so natural, their relationship is magical, each swooning over the other, but then things turn - leading to a big explosion when KOK suggests they might want to wait to have children and Linda slaps him hard across the face - at that point he leaves, and from there after the threat of one or the other leaving is always present in their relationship; Linda becomes especially turbulent during her pregnancy - in one of the many very funny moments in this largely dark novel - dark like a night sky brightened w/ many stars - KOK sees a pregnant woman lashing out at her husband or partner and he thinks: So I'm not alone! What makes this passage through relationship hell so smart and readable, in part, is KOK's clever narrative structure, essentially peeling off layers and moving backward through time - so that as we read of their tempestuous relationship we know, from the opening scenes of the novel, that a few years down the road they will be a boring small-city couple coping with children's parties, diaper changes, child car - and each restless and wondering is this all there is to life? And then, on a broader level, we know that KOK has transform all this diurnal material into a very evocative, challenging, and astonishing examination of life and consciousness - his role as a writer is the gravity that holds this universe together.