Especially trying is Book Six’s 400-plus page excursus into Hitler and the etiology of the Third Reich. It is a grindingly sophomoric exercise that sits undigested under this novel’s skin, like an armchair inside a snake. This section purports to explain why Knausgaard’s book shares a title with Hitler’s “Mein Kampf” — in German, “My Struggle.” But its salient points could have been made in 40 pages, or even four.

I write all this as a Knausgaard admirer. The earlier books in this series, notably the first three, and especially Book Two, were for me among the great reading experiences of this decade. In his commitment to the quotidian details of his life as a boy and as a man, Knausgaard writes like a whale filtering krill. He has an uncanny, nearly magical gift for isolating his details, for holding them to the light until they shine.

What once felt like sorcery in his work now sometimes seems, in Book Six, like fumbling tricks. A spell has been broken, a thermometer shaken down.

It’s simplest to talk about this novel as if it were three 400-page books, which arguably it should have been. In the first, Knausgaard comes to grips with the fame the early books in the series brought him. There is a freight of unwanted attention, especially a threatened lawsuit from his uncle Gunnar, who was incensed that so many family secrets were spilled in Book One. The author smokes and frets and tries to keep writing.

Image Karl Ove Knausgaard Credit... Chester Higgins Jr./The New York Times

The second section contains the Hitler material. It includes a close reading of “Mein Kampf,” and considers that book’s ideas and impact through many lenses — through Dostoyevsky’s consideration of nihilism; Heidegger’s yearning for simplicity; the weird and barbed images of the Old Testament, still lurking somewhere in our minds. He spends pages on a favorite poem by Paul Celan. He winds through the socialism of Jack London and Karl Marx, through the art of Rembrandt and J.M.W. Turner, through Wagner’s triumphal music and Victor Klemperer’s analyses of fascist language. Knausgaard doesn’t bite off more than he can chew, for he chews with a morbid enthusiasm, one that the reader never quite comes to share.