If you are in Barcelona you have some bookshops in English like la Llibreria Anglesa but you also have places like FNAC and CASA DEL LLIBRE where you can buy novels, etc in English.
For some days now we have too http://www.amazon.es. I have read that there is AMAZON PREMIUM and that paying about 15 euros a year you do not have to pay for the sending of the books to your home. I do not know if the list of English books is so big as the one of AMAZON.COM (I imagine that they have a stock of books in Spain so I imagine there are less books or at least less books that one can receive soon …) Anyway, lloking at their website I see that among their English books they have a selection of novels that have been translated into English mainly from Castilian writers.
I put here a list of some of the books I have found: