I'm a Spanish resident and a big lover of Anarchist philosophy and history, although there are quite a few sources to read from, I can't find much on the actual origins of the movement in Spain apart from the Giuseppi Fanelli's tour during the First International, and this surprised me due to how prominent and important anarchism has been and is in Spain.
Spanish anarchism is a relatively popular topic in this subreddit. /u/tobbinator answered here, /u/aquitania provides Spanish-language sources here. More book suggestions can be found in this thread. /u/crrpit has more information here.