For Whom the Bell Tolls — Ernest Hemingway's novel set during the Spanish Civil War remains essential reading for anyone trying to understand the weight of that conflict on the Spanish landscape and psyche.
Homage to Catalonia — George Orwell's account of fighting in the Spanish Civil War, particularly his time in Barcelona and with the POUM militias. Clear-eyed and deeply personal.
The Sun Also Rises — Hemingway again, this time in 1920s Pamplona. The festival of San Fermín is depicted with enough truth that it still feels relevant.
Iberia: Spanish Travels and Reflections — James Michener's sprawling 1968 exploration of Spain. Dated in places but still a generous and perceptive introduction to the country's regions and character.
Driving Over Lemons — Chris Stewart's memoir of buying a farm in the Alpujarras mountains of Andalusia. Funny, affectionate, and a good picture of rural Spanish life.
South from Granada — Gerald Brenan's account of living in a remote Andalusian village in the 1920s. One of the best portraits of pre-war rural Spain.
The New Spaniards — John Hooper's thorough and updated survey of modern Spanish society, politics, and culture. Good background reading before a longer stay.
Carlos Ruiz Zafón's Barcelona quartet (beginning with The Shadow of the Wind) — not travel writing, but Zafón's gothic Barcelona is rendered with enough detail to function as a literary map of the Gothic Quarter.