Abel is a hunchbacked recluse pushing 70. Basic tasks and a bottomless mourning for his lost family mark his days. A real-estate boom makes him a rich man, but the new neighbours want him out. He switches his horse for a car, but such minor concessions to contemporary living are not convincing anybody: he's stuck in the past.

Seth, a 15-year-old science nerd, appears to have more of a future, yet his mother's diagnosis with early onset Alzheimer's casts a shadow over it. He sets out to trace his mother's genetic history, and we know that his story will intersect with Abel's.

As this narrative fusion is pretty much assured from the opening pages of The Story of Forgetting, Stefan Merrill Block's debut novel, the pleasures contained within the book stem from seeing how the stories gradually unfold, rather than from flashy plot twists (though there are several of these). Block's task is ambitious. By examining an ostensibly modern disease, he wants us to consider an ancient condition: the need human beings have to tell stories. To understand his mother's illness, Seth first turns to Science for direction. Ultimately, however, Imagination (represented here by the alternative world of Isidora) is needed to fill the hole left by forgetting.

This cleverly wrought novel has spectacularly launched the literary career of Block, who is only 25, but its success is not unqualified. In places, the book is over-written, too self-conscious and rather dependent on cheap tricks. For every elegant sentence, there is another in which Seth describes, for instance, the "halves of me brewing in my dad's seminiferous tubules and my mum's ovarian follicles". In an effort to make Seth and Abel flesh-and-blood characters, Block also relies too much on their exaggerated physicality: the respective curses of teenage acne and a hunched back. At times, humour and pathos do not so much mingle as strain awkwardly to coexist.

Yet, overall, The Story of Forgetting comes together impressively. The sins of the first-time novelist are regularly counterbalanced by a thoughtful sincerity which gives weight to Block's central assertion that stories provide "something more desperate and more necessary" than other forms of knowledge.