Coming out of the white at me was a woman's face," recalls Anna, haunted by the gradual manifestation on a photographic tray. The reader is spellbound too as "each strip of time" is revealed, "all the way to the far end, where the man's face was like a patch of cloud against night". Emma Darwin's debut is an historical novel with a dual time frame. Anna is a neglected and alienated teenager dumped at a boarding school in Suffolk in the hot summer of 1976. Here she meets two professional photographers, Theo and Eva, who introduce her to an emotional and intellectual world she has lacked. They kindle in her a burning sense of the proximity of the past.

Darwin's second narrator is Stephen Fairhurst, a wounded veteran of Waterloo, whose secret history is gradually revealed. Historical romance, Gothic tale and Bildungsroman, Darwin's novel ponders its own processes, mesmerised by the "strips of time" that layer one another in a place. The narrative centres on the powerful nostalgia of a house in time, within a landscape that records the passage of generations. When Anna ponders Fairhurst's picture, she wonders "for a mad moment" what it would be like if the picture were a two-way window.

The novel, beginning at the Peterloo Massacre, recapitulating the Napoleonic Wars and touching upon the Spanish Civil War, is ambitious in concept and design. Its canvas is immense, and its leisurely and somewhat prolix style relies on the devices of 19th-century realism. On the narrative level, it could usefully have been cut by a third. The author delights in detail and colour, and while this can yield memorable scenes, the urge of the historical novelist to tell you everything she has found out keeps the pace slow.

But if character and dialogue in The Mathematics of Love are often prosaic, the narrative of photography is electrifying. Darwin creates an imaginative language capable of suggesting the quality of the uncanny present in the humblest snapshot.

In the end, history remains mysterious. The magical scene in which Anna first witnesses and participates in developing a photograph captures this world of the unknown in a peculiarly moving way. As the Spanish woman fighter in the photo becomes manifest, Anna craves knowledge. What happened to her? Is she dead? Theo has to acknowledge that "one cannot know".