Scifi novel idea: A habited planet without a sun (these actually exist) with heavy elements and high gravity. The surface unevenness is the best source of energ

Scifi novel idea: A habited planet without a sun (these actually exist) with heavy elements and high gravity. The surface unevenness is the best source of energy. After millions of years of extracting energy from flattening, the planet becomes a perfect ball and all life ceases as there is no energy to be found anywhere.