Roller Coaster World — Kenneth Bulmer

Parsloe's Planet was in its death throes. A world of mobile cities, the populace had moved frantically from radiation site to radiation site - for without this life-giving radiation the inevitable result would be insanity and death.

Now the radiation was failing. Soon it would be no more. The planet was going to die.

But into the chaos and agony of the dying planet comes Douglas Marsden: an outcast, a renegade - and the only man who can save the stricken world.