Mack Reynolds 
Mercenary From Tomorrow 

Is the story of 21st Century Earth – a world where work is forgotten, where the masses fight boredom with trank pills and telly, and where it is almost impossible to leave the social class you were born in. You could break the class barrier only by hiring yourself out as a mercenary to fight in the prime-time wars that are fought to keep the telly-viewing public satisfied. That is the only way to move up the ladder – if you could stay alive long enough.