Norman Lewis was the best not-famous writer of his generation, and a better writer than almost all who were. He was not-famous because of an English prejudice: because critics who judged his works of travel and non-fiction as lower than the yardstick of artistic genius represented by the novel have ignored the truth that over four decades, from the 1950s to the 1990s, he wrote books that have survived better than all but a handful of novels.

A pharmacist's son from Enfield, Lewis (1908-2003) became unmatched as a witness to his times. His account of south-east Asia before the Vietnam war, A Dragon Apparent, remains required reading. Voices of the Old Sea, a glimpse of Spain as it was before the tourists arrived, is a classic in the literature of the Mediterranean. His memoir of wartime Naples, Naples '44, is a masterpiece.

An expert at penetrating the glorious, and inglorious, surfaces of our planet, as a stylist he was a revolutionary, entirely self-taught. In appearance he was someone you could pass in the street without realising anyone had gone by, yet his self-effacing quality, which allowed him to observe unnoticed, concealed extraordinary glamour. For more than twenty years he spied for the British government. He raced Bugattis before the war, lived in Ibiza after it, and was a crack shot, flamboyant host, and businessman with mafia connections, leading a life of such self-pleasing hedonism that his existence at times was closer to a rock star's than anyone else's.

Published to mark Norman Lewis's centenary, Julian Evans's Semi-invisible Man is a fascinating view of a suburban fugitive and adventurer; an incomparable witness; a writer of unsurpassed humour, wisdom and compassion for the ridiculous. It is a biography that aims to send its readers hurrying to the books of an overlooked master.