Spent a great deal of time in Spain when I was in the Air Force and began to read a lot about the history of the country. Then I stumbled upon an old military surplus Mosin-Nagant that has markings identifying it as being used in the Spanish Civil War, so I can recommend this book as one I enjoyed and I see it's available as an Ebook now.
The_Battle_for_Spain
Then there's this book which discusses the overthrow of Russia's government near the end of WWI, though it focuses mostly on the involvement of American troops that were involved.
When Hell Froze Over