Start with Hunger. It came out in 1890, it runs a couple of hundred pages, and it is the book that broke Norwegian fiction open: a starving writer walking around Kristiania, narrating his own mind's collapse in the present tense with no plot to speak of and no redemption at the end.
One condition on that recommendation, and it matters more here than for almost any other author on this site. Do not read the free public-domain Hunger. The English text floating around for nothing dates from the 1890s, and it was cut and softened for the sensibilities of the time — the obscenity, the sexual material and the sheer nastiness of the narrator are all reduced. Later translations restore the original. Check the copyright page and prefer a translation from the last few decades. If your copy costs nothing, it is almost certainly the wrong one.
The obvious alternative starting point is Growth of the Soil, the novel most often named when the 1920 Nobel Prize comes up. It is a fine book and it is further down this list, but it is the least representative thing he wrote — slow, biblical, agricultural — and readers who begin there often conclude that Hamsun is a pastoralist, which is the opposite of the truth.
The early novels
Read these four first, in this order. Hunger, then Pan — a short, lyric, disastrous love story in the far north, told by a hunter who cannot behave like a person. Then Mysteries, the strangest of them: a man in a yellow suit arrives in a small town and systematically dismantles it and himself. Then Victoria, the slightest and most conventional, a straightforward story of class and thwarted love.
These books are the reason Hamsun matters. The interior monologue, the unreliable and self-sabotaging narrator, the refusal of moral resolution — later novelists took all of it from here.
The Nobel novel
Growth of the Soil is a different writer: Isak clearing land in the wilderness, a farm growing, generations arriving. There is no irony in it, which is startling after Mysteries. Read it after the early four, when you can see it as a deliberate turn rather than as a starting position.
The later social novels
Segelfoss Town, Women at the Pump, Wayfarers and The Ring is Closed form the long tail. They are broader, more satirical and more populated, and they take the same suspicion of modernity that made Growth of the Soil warm and make it sour. The Ring is Closed was his last novel, published in 1936. Most readers never get here, and that is a reasonable choice.
The politics, stated plainly
You will encounter this, so here are the facts. Hamsun supported the German occupation of Norway from 1940. He met Hitler in 1943. In May 1945 he published an admiring obituary of Hitler in a Norwegian newspaper. After the war he was detained, subjected to psychiatric examination, and ultimately fined rather than tried for treason. On over-grown paths is his own account of those years, written in his late eighties.
What to do with that is genuinely contested, and readers land in different places: some cannot separate the work from it, others note that the novels that made his name were written half a century earlier. This guide is not going to settle that for you. What it will say is that On over-grown paths should be read last, and read for what it is — his account, not a neutral one.
Where to stop
Three books is a full Hamsun for most readers: Hunger, Pan and Growth of the Soil. Add Mysteries if the first two work on you. The late social novels are for readers who have already decided he is worth the time.
For the parallel revolution in interior narration happening in the same decades, see James Joyce.
Follow the full ordered path here: Knut Hamsun Reading Order: Where to Start.
