Lenin’s Tomb by David Remnick is another very good book on the subject.
Honestly, I’m not sure if anyone beyond the old line Communist conservatives was really willing to fight for the way things were in the USSR - they either wanted a return to the Good Old Days (either the Tsar’s Good Old Days or Stalin’s) or just a complete new state. Moderate communism was doomed, so I suppose a civil war would have to see the republics splitting off and people completely rejecting the Gorbachev consensus.