At the eve of the big show down between two clubs, I figure I'd toss this question out. I've always heard about how the rivalry between the two is a reflection of the cultural and political divides in Spain. However, it's always very fuzzy to me, presumably because all the talks assume the audience has adequate knowledge of Spain's history, which I don't have. Therefore, I am wondering if anyone could point me to a good source (book, website..etc.) in English that explains things for a foreigner with limited understanding of the social, political, cultural, and historical context of the rivalry. Thanks in advance.