A combination of by chance reading For Whom the Bells Toll and playing Hearts of Iron IV at about the same time has left me very interested in the Spanish Civil War. I have an ~2 week mostly internetless vacation coming up and I'm looking to gather some stuff to read or listen to. So far I've found this archive from Birmingham Young University which I could download or print the documents and Episode 12 of the Ask Historians podcast.
Does the Birmingham archive have good information? Are there any really good (relevant) books I should bring with me? Is the Spanish Civil War just a boring waste of time? Please help.
I took a look through the Books and Resources list, but was unable to find anything. In this thread The Spanish Civil War by Antony Beevor is suggested by [deleted], but I don't know its reputation. Also, based on flairs, paging /u/tobbinator, /u/Domini_Canes, and /u/k1990
One good primary source on the Spanish Civil War is George Orwell's Homage to Catalonia. Orwell actually fought in one of the militias and and has on the ground experience because of this. He also wrote about the bigger picture that was going on outside of his knowledge at the time.
I wrote my A Level (age 16-18) coursework on the British government's response to the Spanish Civil War. It was over 10 years ago so most of this is from memory and my focus was a bit different to yours, but:
George Orwell's writing on it (Homage to Catalonia and also an essay in one of his collections) started me off on this path.
Laurie Lee also wrote A Moment of War about his time in the International Brigades.
Anthony Beevor's The Spanish Civil War (suggested above) was good background reading.
If you happen to be London-based then there are loads of great primary sources in the National Archives - my research skills weren't very well developed at the time but I managed to find lots of interesting bits and pieces including cabinet discussions on whether the British government should be responding, letters between Churchill and Anthony Eden complaining that the British government wasn't responding, and (perhaps more relevant to your interest) contemporary reports on the situation written by Spain-based diplomats. I believe you can get copies of records made but suspect it's a bit pricey, so:
Here is a an academic site which points to lots of UK-based primary sources available online: https://archiveshub.jisc.ac.uk/features/spanishcivilwar.shtml
I hope some of this helps. I think it's a fascinating topic and definitely not a waste of time. In the historical context it's especially significant - a democratically elected European government was successfully overthrown by fascists, Nazi Germany helped out and got in some early bombing practice, and the European establishment basically shrugged its shoulders and said 'not my problem.'
Jon Cowans's Modern Spain: A Documentary History remains the best collected volume of primary sources published in English. To be honest, there is a huge shortage of primary source publications on Spain in the twentieth century. You should also consider "The Anarchists of Casas Viejas" by Jerome Mintz, an oral history but for practical purposes, a good compendium of primary sources.
As far as secondary sources, well, they are endless. In English, some to consider:
Paul Preston, The Spanish Civil War: Reaction, Revolution, Revenge
Adrian Shubert and George Esenwein, Spain at War: the Spanish Civil War in Context
Stanley Payne, The Spanish Civil War