One day in the summer of 2006, writer Arno Geiger drove from his home in Vienna to the village of Wolfurt in Austria's westernmost region. There he met his father who, the following day, would turn 80. Age had not withered August Geiger physically; however, for more than a decade Alzheimer's had been steadily eroding his mental faculties.

When Arno told him that they were going to celebrate his birthday in Wolfurt's church hall, August replied, "I've always liked visiting Wolfurt." But August was no visitor: He had lived there all his life. Soon he wouldn't just have problems remembering where he was, but would also fail to recognize Arno as his son.

"The Old King in His Exile" is a moving memoir that lays bare the cruelty of a terrible illness but also the love at the heart of a father-son relationship. Beautifully translated from the German by Stefan Tobler, the book offers a candid and thoroughly unsentimental depiction of dementia.

As Arno Geiger traces his father's decline, he highlights the frustration and anguish the pair of them endure, together with the bouts of happiness and flickers of hope that bring them closer.

Geiger reveals that it was difficult to ascertain whether his father's initial slip-ups were merely quirks resulting from his eccentric nature or signs of something more serious. But then came problems with socks — storing them in the fridge, or putting them on and wondering where the third one was — and undue stress with easy everyday tasks, at which point August's family faced up to reality. Geiger was forced to take action: "As my father can no longer cross the bridge into my world, I have to go over to his."

That world proved to be a tough place for both sufferer and caregiver. Geiger describes his father's disorientation at home and his confusion with people. Oddball antics are eclipsed by more disturbing behavior: "feeding" a newsreader on TV, asking after dead relatives, searching the house in the middle of the night for children who have long since flown the nest. Geiger sits by helplessly, "watching my father bleed to death in slow motion."

But he doesn't die. Geiger informs us that he wanted to write his book while August was alive, for he, "like everyone else, deserved to have an open-ended destiny." Geiger shows him in healthier times, as a conscripted soldier during the war and a mismatched partner in a marriage. We also see him bonding with his son in joyful moments that are "all the more special because they were wrestled from the illness."

When August banishes his doubt with a smile and tells his son, "You're my best friend!" it is hard not to be touched.

This book could have been a catalog of despair. Instead it is an affectionate portrait of a weakening man and a valuable source of wisdom and comfort.

Malcolm Forbes has written for the Times Literary Supplement, the Economist and the New Republic. He lives in Edinburgh, Scotland.

The Old King in His Exile
By: Arno Geiger, translated from the German by Stefan Tobler.
Publisher: And Other Stories, 192 pages, $16.95.