Im looking for a book that doesnt involve too many stories of people, more fact based with historical argument on the socio economic scene.
Sheila Fitzpatrick is perhaps my favorite author on early Soviet Union. The Russian Revolution is a great overview, and Education and Social Mobility in the Soviet Union explores the functioning of society through one particular function in a very interesting and insightful way. What ever you get, I believe you can't go much wrong with Fitzpatrick.
The Soviet Experiment by Ronald Suny
Edit: It is not solely focused on 1920-1950 but is still a good read.
Life and Fate by Vasily Grossman