The First Men in the Moon by H.G. Wells

A scientist and a businessman travel to the Moon using a gravity-defying substance and discover an underground civilization of insect-like beings called Selenites. As they explore the alien society, the two men clash in temperament and goals—science versus commerce. When things go wrong, only one of them manages to return to Earth. The plot combines adventure, satire, and imagination, questioning imperialism and human nature. It’s a pioneering tale of extraterrestrial exploration.