My Family and Other Animals by Gerald Durrell (1956) — The definitive book about Corfu, describing the years 1935–39 when the Durrell family lived on the island. Gerald was ten years old and spent his time collecting lizards, snails, and scorpions while his older brother Lawrence wrote poetry. Hilarious, warm, and specific about the island's landscape and people. Durrell describes a Corfu that has largely disappeared, but the landscape still fits the descriptions.
Prospero's Cell by Lawrence Durrell (1945) — The older brother's account of the same years on Corfu, written with the solemnity that three wars and a serious literary career had brought him. More reflective than Gerald's version and more interested in the history and mythology of the island. The two books together give an extraordinary picture of pre-war Corfu.
The Magus by John Fowles — Not set in Corfu but in Greece, and drawing on Fowles's experiences in the Greek islands in the 1950s. A useful introduction to the atmosphere of a very different Greece from today's tourist version.
Corfu: Portrait of an Island by James Chatto and W.L. Martin — A more recent travel memoir describing a year lived on the island, with more practical observations than the Durrells and a clear-eyed view of how the island has changed.