In the spring of 1937, Norman Lewis spent two months in southern Arabia spying for the British government. It was an encounter that would make a profound impression. He found an alternative to the moribund conventions of English life and, like others before him - Thesiger, Jack Philby, TE Lawrence - felt the threads that bound him to home broken by the experience.

Lewis commemorated this journey in print three times, yet as Julian Evans notes in his masterly biography, it is impossible to reconstruct accurately what happened, as he was always an unreliable narrator of his own experiences. His journeys may have elicited some of the most celebrated travel narratives of our times but, for the biographer, their contradictions, evasions and frequently embroidered set pieces pose a problem.

Thankfully, Evans's aim is not to quarrel with Lewis's inconsistencies. For him, Lewis was a writer of the "Romantic stamp", who realised "meaning and truth are a scattered dissemination of signifiers, and that the writer's job is to take advantage of that". The result is a brilliantly researched and sympathetically told life story interspersed with probing meditations on how memory and stories play with the facts of our lives.

Lewis was a late developer as writer, though his "escapist reflex" was honed as a child in Enfield, where he was bullied. This instilled in him the creative desire "to make for somewhere else that was as else as could be".

Still, it wasn't until two decades after the publication in 1935 of his debut travelogue, Spanish Adventure (which he later disowned), that Lewis properly fulfilled his literary ambitions, though the onset of the second world war yielded the subject matter for his celebrated wartime memoir Naples '44. Thereafter he cultivated the talent for semi-invisibility honed during his youth, observing unnoticed the extraordinary landscapes and peoples of the countries in which he travelled. In the retelling of his life, one could not hope for a more sympathetic or intelligent guide.

Semi-invisible because he "was absolutely dead against publicity" - a risky tactic that might have worked for JD Salinger and Thomas Pynchon but sadly backfired for Norman Lewis (1908-2003). Yet Graham Greene once described him as "one of the best writers, not of any particular decade, but of our century". Though he wrote novels, he is best known for his travel books, such as A Dragon Apparent: Travels in Indo-China, Naples '44 and Voices of the Old Sea. In this authorised biography, Julian Evans, Lewis's friend and editor, compares the author's diaries and notebooks with the writing to show how he often embellished the truth - a process of "creative recollection". This is an erudite, slightly self-conscious biography by a man who feels the weight of his responsibilities, so you might want to discover the writer himself before tackling this well-written and exhaustive life. Lewis, a restless, randy character, never lost his contempt for his native Enfield, and brilliantly personified what Baudelaire called la haine du domicile et la passion du voyage.