Barcelona by Robert Hughes (1992) — the art critic's account of Catalan history and culture through its art and architecture. Dense and opinionated, it gives Catalonia's particular identity a depth that makes the Romanesque churches and the medieval quarters mean more. Hughes has no patience for the picturesque; he wants you to understand what you're looking at.
Homage to Barcelona by Colm Tóibín (1990) — a personal, literary portrait of the city and the region written in the aftermath of Franco. Tóibín travels from Barcelona into the Catalan countryside and pays sustained attention to what Catalan identity means in practice. A good companion for anyone travelling beyond the capital.
Voices of the Old Sea by Norman Lewis (1984) — Lewis spent three years in a fishing village on the Costa Brava in the late 1940s, and this account of traditional coastal life is one of the best things written about Spain in the 20th century. The Catalonia he describes — poor, suspicious, tenacious — is not the Catalonia of the tourist brochures, and is all the more valuable for it.
Romanesque Art in Catalonia — several academic editions exist. Catalonia has one of the densest concentrations of Romanesque architecture in Europe, and a compact reference guide to the style — what makes a double apse unusual, why the bell towers look the way they do — sharpens the eye considerably in towns like Besalú.