Here are some useful resources on Modernisme, the Catalan version of Art Nouveau:
To start with ...
- The CulturCat site is informative, but the English version has an autotranslate feel to it.
- Gaudiallgaudi has plenty of information, though the English versions are sometimes unreadable.
- Ruta del Modernisme contains historical background and has links to all the major buildings. The book of the same title is well worth buying and takes you to places beyond the usual tourist routes. (There is an underground shop where tours can be booked beneath the Plaza de Catalunya.)
- The Generalitat produce a colourful pdf guide to the major works in the Modernist style in Barcelona and beyond: Modernism: Art Nouveau in Catalonia
- The Barcelona Modernista site (in Spanish), constructed by an individual enthusiast, is excellent.
- The Anglo-Catalan Society publishes a monograph by architect and architectural historian David Mackay, Modern Architecture in Barcelona (1854-1939)
- Finally, the blog on Catalan architects gathers a lot of good material, overwhelmingly in Catalan.