Maine specialised in a specific sort of science fiction - he'd take a single scientific fact (or premise) and then extrapolate it until it reached the most dismal possible conclusion. As a result, over the course of 25 years, he destroyed the world in a thousand innovative ways.
The protagonist of Calculated Risk is Phil, a scientist from the distant future. He lives in the radioactive squalor of post-Armageddon London with his mistress, Kay. Fortunately, Phil has an escape route. Using quantum chicanery, he transports the minds of Phil and Kay into the past (1960s London). Two mid-century Londoners are brutally ejected from their own bodies, and Phil and Kay take over.
Brilliant - and quantum - so what could possibly go wrong?