Considered one of the fathers of the modern short story, his surprise ending and clever plot structure that easily led to the denouement served as models for writers such as O.Henry and W. Somerset Maugham (enotes). His works are characterized by an economy of style that yet has a precision to the details revealed.
Certainly he influenced other writers in the realistic depiction of the futility of war and in the unsympathetic portrayal of society. He especially focused on the pettiness the Normans and the civil servants of their area, a characteristic he observed as a civil servant when he was a young man.
His interest in the new science of psychology led him to examine what motivates people and what strange ideas trouble the minds of individuals as well as supernatural phenomena. In fact, this obsession with the inner workings of the mind, along with his syphilis, brought Maupassant himself to insanity. But, his interest has had a profound effect upon modern writers such as H.P. Lovecraft.
Similar to Poe, there is an intensity to Maupassant's works. In Leo Tolstoy's essays, he writes of Guy de Maupassant:
Maupassant evidently possessed ... an intensified, strained attention to details ... he was able to see something new, something which others did not see.