Gateway
Swept the Hugo, Nebula and Campbell awards. Routinely listed among the best SF novels ever; the prospecting-the-incomprehensible premise echoes everywhere from Roadside Picnic comparisons to modern 'big dumb object' fiction.
Series Guide
Heechee Saga
Pohl's sequence beginning with Gateway: humanity rides the abandoned starships of the vanished Heechee, gambling lives on destinations no one can predict.