Gateway (1977)

Robinette Broadhead gambles on journeys in alien ships whose destinations humans cannot control. The technological mystery is inseparable from poverty, fear and the aftermath of choices he struggles to discuss. Pohl alternates dangerous expeditions with therapy, giving guilt as much weight as discovery. Moderate technical demands, with the workings of the inherited technology deliberately uncertain. It opens the Heechee sequence but centres a forceful personal reckoning of its own.