Honestly this one is hugely dependent on who you ask. Keep in mind this is fairly recent not even 30 years ago, history takes a while to draw a conclusion. Some point to Reagan’s military build up in the US destabilizing the USSR economy others say that the USSR economics was bound to fail. Some point to Gorbachev and his progressive policies to free the Eastern Nations. But in short around the 1990s the USSR decided no longer to enforce the communist regimes implemented in the Eastern Nations and these nations eventually drifted to more democratic platforms. Russia would eventually succumb to this as well with Gorbachev’s progressive leadership making new capitalistic like policies plus helping the liberties of Russian citizens. No whether or not Russia has become a true free nation remains to be seen but basically that’s what happened that’s a really short and shallow over view though from a person who has close to a bachelors degree worth of knowledge in history so maybe some fellow history buffs could help out

TLDR: The USSR economy became to unstable to enforce Eastern European regimes and the cause of the Unstableness is still up for debate

There's an FAQ section, "The end of the Soviet Union" . But the general discussions there, like a lot of other 5-year-old answers, don't appear to be thorough on the historiography or even on the common arguments going around, and one has standard Web arguing style, so I can't really recommend them.

The best I can see there is "How to research what led to the collapse of the USSR?" , which gives suggestions for how someone might ask a university research historian. There is a book recommendation by /u/facepoundr .

There's a look at the economy in general in "I’ve read that USSR was extremely inefficient in its industry and agriculture" [&c] by /u/true_new_troll , and the book mentioned in the original question I've seen mentioned elsewhere.

I hope that this doesn't discourage you!