Not the famous 17th-century poetic travel-ogue of the same title by Japanese master Basho, this is Australian novelist Flanagan's take on the same motif of love's durability and elusiveness.
It's told mostly by Dorrigo Evans: philanderer, Lord Tennyson buff, doctor and commanding officer in a Japanese POW camp, and subsequently an oncologist of erratic skill.
Coming from a dusty little settlement in rural Tasmania, Dorrigo sees his first fighting against the Vichy French in Syria. After the calamitous capitulation at Singapore, he endures appalling journeys by train, truck and on foot through the jungle, to a camp where English officers insist that British stoicism and pluck will ensure their survival.
The said officers soon die. The Australians labour on the Burma Railway, watching their own bodies decay and disintegrate, while Dorrigo does what he can to keep some alive.
You won't - you can't - forget the ulcer hut, the ceremonial beating to death of one prisoner, the amputation of a gangrenous thigh.
Dorrigo does astonishing things. Through his eyes, we see acts of blasphemous tenderness among the skeletal prisoners, along with other acts of dreadful self-preservation.
The war ends. One of every three Australian prisoners who slaved on the railway is dead.
The others come home to partners who can't understand, the near-irrelevance of war crimes tribunals, trauma and alcoholism and years when men mustn't weep.
Dorrigo lives to see himself and others praised "for things not worthy of praise", to mourn old loves and drift into new, semi-satisfying ones, to try to unpick experience from mythology.
There's no simplistic good-versus-evil equation in this deeply unsettling novel. Flanagan acknowledges and explores the complexity of all his characters. A brutish, brutalised Korean guard and a homicidal, haiku-declaiming Japanese colonel have their own mutilated idealism. The post-war story of another Japanese officer, scrabbling among Tokyo's ruins for firewood, keeps challenging perceptions, as does the tension between Dorrigo's surface and interior lives.
The plot crosses decades in a page or a paragraph. It's a collage and occasionally a confusion, stuffed with graphic detail: a face in firelight, "gleaming bright as a freshly turned out plum pudding"; the smell of disappointment in a shabby hotel; a detailed account of the aesthetics of decapitation. Not many events pass without a symbol or three.
Events storm through the post-war decades towards a conclusion with bushfire, a veteran corrected by journalists and documentary-makers, a column of Japanese boy soldiers passing, a car crash and the dreams that follow. It's a cram 'til the very end.
It's also a relentless and relentlessly searching story of the evils men do to each other, along with the loves that come with equal force and fearsomeness.
The Narrow Road to the Deep North by Richard Flanagan (Vintage $37.99).