The Bitter Pill — A. Bertram Chandler

To Paul Clayton, obscure shipping clerk, his forty-fifth birthday was not an occasion for celebration. It meant the achievement of status of Senior Citizen, and with it several dubious privileges - not least of which was voluntary euthanasia, facilitated by the government issue suicide pill. Those who changed their minds, once they had broken the capsule containing the lethal pill, faced the prospect of forced labor camps in the Australian desert of the penal colony on Mars, where convicts toiled to make more space fit for Earth's over-spilling populations.

Under the supervision of the corrupt and brutal Mars Corps, Clayton crosses paths again with others he once knew on distant Earth. They find themselves caught up on a maelstrom of terror and political intrigue.