Everything I find on this ex-country is either extremely anti-USSR (eg. little black book) or overly pro-USSR (eg. Why Women Have Better Sex Under Socialism). Things that take a more neutral approach tend to just focus on the politics and why the leaders acted the way they did.
I found Class Theory and History: Capitalism and Communism in the USSR quite interesting, though it didn't go into history quite as deeply as I'd hoped. Other, deeper books tend to focus on one particular point (almost always the revolution itself)
I know it's impossible to get a totally neutral perspective, I'm really just looking for something that's more nuanced.
'Second-hand time', by Svetlana Alexievich. The book consists almost entirely out of the memories and opinions of people who lived in the Soviet Union. So it's not from the era itself, but it's very interesting and raw. (Not melodramatic or something, it's more in interview style except you rarely see a word from Alexievich herself; whom is actually a journalist. So the people talk very freely.)