The following are some suggestions coming from reading Chomsky (a more comprehensive list)

Borkenau, Franz The Spanish Cockpit
Brenan, Gerald The Spanish Labyrinth
Broué, Pierre and Temine, E. The Revolution & War in Spain
Jackson, Gabriel The Spanish Republic and the Civil War 1931-39 1)
Malefakis, Edward Agrarian Reform and Peasant Revolution
Peirats, J. Anarchists in the Spanish Revolution
Rocker, Rudolf The tragedy of Spain

Shanin, TeodorLate Marx and the Russian Road1)

Avrich, Paul The Russian anarchists 1)
Bell, Daniel The End of Ideology (here the talk on Machajski and his critic of intellectuals, see Sergio Leone, “Once upon a Time the Revolution” and this piece by Avrich) 1)
Shanin, Theoror Late Marx and the Russian Road