Though it was not long ago, I can't remember when I first heard the whisper in the literary sounding-room: that a Norwegian writer, more or less my age, had belched out a brooding six-volume autobiographical sequence of novels under the provocative title "My Struggle"; that it had taken his national literature by storm and he was being read and gossiped about as avidly as JK Rowling at Pottermania's apex.

I must have read two or three reviews or mentions of Karl Ove Knausgaard's novels before I happened across the first volume, A Death in the Family. Of course it seemed preposterous: the vast claims, comparisons to Proust, the peculiar specificity of Norway – when had I last read a living Norwegian? Had I ever?

First rumours of a previously unknown great writer invariably feel like a hoax – I remember when word of Roberto Bolaño slipped out, 15 years earlier. Resistance is aroused, for a writer, in the form of rivalrous scepticism. As a reader, one suffers the dread of disappointment, the reluctance to glimpse a naked emperor. Yet for me, from the very first page, all doubts or pre-emptive weariness evaporated, replaced by the oxygen-blast of this vast novel's absorbing tone of remorseless, questing curiosity towards the problem of existence.

The book investigates the bottomless accumulation of mysteries everyday life imposes, from the vantage of a helplessly undisguised narrator: a stroller-dad, navigating a mundane world of nappies and tantrums on train platforms, who suspects he is the possessor of literary genius, and finds these selves bitterly incommensurate. He is also a father enmeshed in the earlier selves that delivered him to this present one: a pensive son of a depressed drunkard, a friend, a citizen, a subject of global modernity.

Knausgaard's approach is plain and scrupulous, sometimes casual, yet he never writes down. His subject is the beauty and terror of the fact that all life coexists with itself. A living hero who landed on greatness by abandoning every typical literary feint, an emperor whose nakedness surpasses royal finery. I can't wait for the translator to finish the last three volumes.

• Dissident Gardens by Jonathan Lethem is publishedby Jonathan Cape.