This book by Warren Carroll* of Christendom College is a great short history of the Spanish Civil War from a Catholic perspective. The stories of the martyrs of Spain contained within are incredible. Dr. Carroll’s perspective is slightly less critical at times than I’d like to see. He does acknowledge the failings of the Nationalist side, but at times goes a bit far to excuse them.
*Interestingly, Dr. Carroll also went to Bates College.