Dragon’s Egg

Set on a neutron star whose surface gravity is some 67 billion times Earth's, Robert Forward's hard science fiction novel imagines the cheela, sesame-seed-sized intelligent beings that live and think about a million times faster than humans, so that one Earth hour equals hundreds of their years. The star, called Dragon's Egg, is detected by astronomers in 2020, and a human expedition is later sent to observe it from orbit. Forward tries to convey unfamiliar ideas and scenes while giving due weight to known scientific principles. It was published in 1980.

Andrej Karpathy found it a highly inventive and fascinating alien contact story, though he thought it ran a little long.