Really enjoyed Dragon's Egg about life on a neutron star.
> The adults of the star's most intelligent species, called cheela (no flexion for gender or number), have about the same mass as an adult human. However, the extreme gravity of Dragon's Egg compresses the cheela to the volume of a sesame seed,[2] but with a flattened shape about 0.5 millimeters (0.020 inches) high and about 5 millimeters (0.20 inches) in diameter. Their eyes are 0.1 millimeters (0.0039 inches) wide. Such minute eyes can see clearly only in ultraviolet and, in good light, the longest wavelengths of the X-ray band
> By humans' standards, a "day" on Dragon's Egg is about 0.2 seconds