When worlds collideKamila Shamsie's epic new novel will challenge and enlighten its readers, writes Maya Jaggi

The huge ambition of Kamila Shamsie's fifth novel is announced in the prologue. As an unnamed captive is unshackled and stripped naked in readiness for the anonymity of an orange jumpsuit, he wonders: "How did it come to this?" The vastness of the question as applied to a prisoner in Guantánamo is a challenge to which this epic yet skilfully controlled novel rises in oblique and unexpected ways.

Unfolding in four sections, the novel traces the shared histories of two families, from the final days of the second world war in Japan, and India on the brink of partition in 1947, to Pakistan in the early 1980s, New York in the aftermath of 11 September and Afghanistan in the wake of the ensuing US bombing campaign. At its heart is the beautifully drawn Hiroko Tanaka, first seen in Nagasaki in August 1945 as a young schoolteacher turned munitions factory worker whose artist father is branded a traitor for his outbursts against the emperor and kamikaze militarism. She falls in love with a lanky, russet-haired idealist from Berlin, Konrad Weiss, with whom she shares - along with other key characters - a love of languages. But their romance is curtailed by the flash of light that renders Konrad a shadow on stone and burns the birds on Hiroko's kimono into her back, a fusion of "charred silk, seared flesh".

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The identity of the Guantánamo captive remains unclear till the powerful denouement, as events unfold with a malign logic whereby even a man's stooping for a cricket ball can be fatally misconstrued. Any reader anticipating a predictable yarn about the radicalisation of Islamist youth may feel cheated. Far more, I suspect, will feel challenged and enlightened, possibly provoked, and undoubtedly enriched.