This is the book to read for all the gory details of the twilight years of the Soviet Union. I know of no other source which has anywhere close to the same access to primary sources and day-by-day capture of specific events. A lower fidelity history will write "Bush and Gorbachev had a phone call but were unable to agree on terms for restructuring soviet debt via bridge loans." Zubok revels in the absurdity and flippancy of the rich details and the size of the disconnect, and goes deep into transcripts, so will instead get the exact dialog of the transcript, where Bush asks Gorbachev what happened to the last batch of loan money.
It's incredible to see the exact dialog where Gorby casually says that all that money disappeared, he doesn't know where it went, and it's not important to the big picture. C'mon man, we're trying to build socialism with a human face here, not balance a checkbook! This account very effectively captured that Gorbachev was not personally corrupt and stuck to his democratic socialist rule of law ideals which allowed him to be outmaneuvered in a way which unleashed a chaotic and destructive process that he had the power to clamp down on but refused.
Goodnight sweet premier, and flights of pensioners scream thee to thy grave.
Then there is the matter of Yeltsin, a figure who would've been universally loved if he had died in 1990, but as it is, comes off as someone who is not nearly hated enough for what he did to his countrymen through staggering ambition and even less ability than Gorbachev to understand the details of his own policies.

I just got a copy of this after seeing this book pop up a couple times here. Thanks!