A science fiction novel set in the year 3000, when Earth is an empty wasteland full of aliens, and one man decides to marshal the survivors to rid Earth of the alien invaders.
I was in my "if its a big book it MUST be good phase" when I saw this in a remainder bin, having remembered my favorite science fiction author R. A. Heinlein mentioned Hubbard as being part of the then "golden age" of writers, I liked the book...
kinda out there as a POST Apocalyptic story I liked Frank Herbert's The White Plague
about what might drive a man to bring about the ruination of the world...
and also War Day by Whitley Strieber and James Kunetka which might be a more realistic (for 1984) scenario the aftermath of a limited nuclear exchange http://en.wikipedia.org/wiki/Warday
and for a more hands on.. there's always playing fallout3