A Winter on the Nile, By Anthony Sattin

In the wrong hands, the chance discovery that Florence Nightingale and Gustave Flaubert took the same boat up the Nile on a day in November 1849 could have yielded a speculative novel or sub-Stoppardian play. Would Flaubert have been intrigued by Florence's phlegmatic ways and wide-eyed idealism - and what might the 29-year-old Englishwoman have made of the novelist's taste for hookahs and harems?

Anthony Sattin takes a more austere and productive approach. The two may have started their journey on the same Cairo barge, but there is no evidence they ever met other than, as Sattin puts it, between the sheets of his book. Instead, he focuses on how Egypt changed their lives.

Both arrived there in their late twenties, yet to embark on their respective careers. Flaubert began Madame Bovary on his return to France; Florence travelled to Scutari for the Crimean War a few years later and became famous.

But the young woman in Egypt was insecure and unknown. She had left a marriage proposal and anxious parents behind, as well as a society that deemed nursing tantamount to prostitution. Her "first footfall in the East", as she described Alexandria, yielded excitement and freedom, with its dancing and nights at the Opera. She disguised herself to visit a mosque and was impressed by the hospital ward of the Sisters of Mercy.

Flaubert was less interested in visiting convents. With his louche travelling companion, Maxime Du Camp, he cast a cold eye on Egyptologist enthusiasms, ignoring the Rosetta Stone and the Pyramids, but "gulping down a whole bellyfull of colour, like a donkey filling himself with hay". He too had arrived lacking in confidence, with a failed attempt at one novel and a domestic life confined by responsibilities for both his mother and his niece.

Sattin's book reminds us above all of the transformative power of travel - ridding yourself of the problems of home to find a new direction. When a traveller's dehabiya sets off from Cairo, it first backs down the Nile with the current; the moment when the sails then fill and the boat heads up south is described by Sattin as unique, "however great your experience of sailing, of rivers, of Africa, whatever you have just done or said or thought, if you are in anyway alive to new experience".

Both his travellers were receptive to such new experience. For this odd couple, their parallel journey proved a turning point. Florence gained the courage to become a nurse; Flaubert took perspective from the "immense, pitiless Orient", and applied it with detached rigour to provincial France. In Egypt he learnt "to understand everything by contrast, where splendid things gleam in the dust".

It is a tribute to Sattin's knowledge of Egypt and his skill as a writer that he makes this counterpoint narrative seem so effortless. His protagonists circle without ever touching in a dance through the desert. Only once do they ever get close: when Flaubert is shown the imprint of a woman's boot in the sand at the caves of Lycopolis and told that it is that of "an Englishwoman who had passed by a few days before". You couldn't make it up.

Hugh Thomson's 'Tequila Oil: Getting Lost in Mexico' is published by Phoenix