Book Of A Lifetime: Red Shift, By Alan Garner

As a teenager, in the mid-1980s, I picked up Alan Garner's 'Red Shift'. It looked like other Garners I had read: a children's fantasy. But 'Red Shift', with its passionately bickering adolescent lovers and its vertiginous plunges through the wormhole of time, shook me to the core every time I read it, and still does.

Garner's novel is by turns unnerving, distressing and romantic. It is formed from jagged pieces of three stories. In the last days of Roman Britain, the renegade Ninth Legion attempt to survive by going tribal; in the 1640s, a village couple await an invasion of Irish Royalists; in a 1960s caravan park, two penniless teenagers try to shield their love from the prurient interference of the adult world.

The most obvious link between the three stories is the cruelty of war. Vietnam never needs to be named; the renegade Romans use the slang of American GIs lost in those jungles. What draws the stories together is not any crude time-travel conceit but key notions - loyalty and betrayal, bloodlust and sanctuary, home and homelessness - as well as a talisman (a Beaker-period votive axehead), and, above all, the landscape of southern Cheshire. You expect it to be the sensitive modern Tom who is haunted by his bloodstained ancestors, but it is the second-century Macey and the 17th-century Thomas who are driven demented by premonitions of the 20th-century boy.

In all three stories, strong women, guardians of the sacred (including sex), try to hold onto – and hold together – broken, "berserk" men. This motif is said to be inspired by Tam Lin, rescued from the fairies by his true love.

The pared-down, enigmatic dialogue and fractured stream of consciousness in 'Red Shift' demands to be read more as poetry than prose. The style reminds me at times of the all-pervasive dread in Shirley Jackson's ghost stories, at others of the tense exchanges in Harold Pinter's plays, at others of Alan Bennett at his funniest. ("You great wet Nelly," Tom's father tells him. "You're about as much use as a chocolate teapot.")

Inspired by a graffito Garner glimpsed at a railway station – "not really now not any more" – this existentialist novel assumes that everything dies, and "it's a pretty mean galaxy". 'Red Shift' has a pagan sensibility but even the Roman soldiers paraphrase Genesis 13:8: "let there be no strife, for we are brothers". Somehow the continuities console; the pattern repeats, and love just might win next time. The novel ends with a two-page letter encrypted using Lewis Carroll's code.

Garner, who was awarded an OBE in 2001, lives with bipolar disorder, and this slim masterpiece is in the tradition of mad kings Sweeney and Lear; a message from the frontiers of pain. More than any orthodox work of historical fiction, it was this weird fantasy novel which taught me to look beyond the walls of my own era, my own reality. Garner makes the past numinous, terrifyingly real: anything but passed.

Emma Donoghue's Man Booker-shortlisted novel 'Room' is out in paperback from Picador