There's a good account of the coup attempt in The Dead Hand[0] in the last 1/3 of the book. According to it, Gorbachev and family were isolated in his dacha, and his "Nuclear Football" -- the Cheget, that controlled their ICBM launch codes was taken from him.

[0] http://www.amazon.com/Dead-Hand-Untold-Dangerous-Legacy-eboo...

I've been learning more about the Cold War and reading stories like this in _The Dead Hand_.

Not a bad read for the historically-inclined: http://www.amazon.com/Dead-Hand-Untold-Dangerous-Legacy/dp/0...