>>7296649books:
The Human Condition, by Andre Malraux
For Whom the Bell Tolls, by Ernest Hemingway
also, i live in catalonia. i'll try to explain you the differences as best as i can.
UGT (Unión General de Trabajadores/General Workes Union) --> A socialist union very much connected with the PSOE (the main spanish socialist party). It was, in fact, the union who radicalized their positions. They supported revolutionary actions in all of Spain during the Second Spanish Republic.
CNT (Confederación Nacional del Trabajo/Nation Workers Confederation) --> Anarchosyndicalist union. In Catalonia they had huge support (up to 2 million affiliates, in a territory wich now has 7, so go figure), and they were the most combative faction from the left i all those years. Also, when Franco made the coup, they were the ones in Catalonia who took to the streets and were able to frustate it, in front of a paralized catalan goverment. Basically, during the first moments of the war, they controled the goverment, and promoted communal forms of organization.
PSUC (Partit Socialista Unificat de Catalunya/Unifies Socialist Party of Catalonia) --> An specfic socialist party of Catalonia. You can count them as a kind of PSOE, but with the addition of the catalan national issue.
You have read the book from Orwell, so i'll not get into the conflicts between them.
hope it helped