H. G. Wells 
First Men in the Moon [PDF ebook] 

H. G. Wells’ 1901 science fiction novel The First Men in the Moon tells the story of a voyage to the moon by Mr. Bedford, a businessman plagued by financial problems, and Dr. Cavor, a brilliant and somewhat eccentric scientist. On arrival they discover that the moon is already inhabited by an advanced underground civilization of insect-like beings who they call "Selenites". This forward-looking novel, critical of the imperialism of Wells’ time, looks at the clash of civilizations and suggests a reflection of how humanity might develop in the future.