H. G. Wells 
Star-begotten 

Star Begotten is a 1937 novel by H. G. Wells. It tells the story of a series of men who conjecture upon the possibility of the human race being altered by Martians to replace their own dying planet. The protagonist of the story Joseph Davis, who is an author of popular histories, becomes overtaken with suspicion that he and his family have already been exposed and are starting to change.