Unknown was, along with Weird Tales, an important early influence on the fantasy genre.
  In the foreword to From Unknown Worlds, in 1948, Campbell commented that fantasy before Unknown had been too much infused with "gloom and terror"; his approach in Unknown had been to assume that the "creatures of mythology and folklore" could be characters in an amusing tale as easily as they could be made part of a horror story.
Horror stories, he said, had a place, but "horror injected with a sharp and poisoned needle is just as effective as when applied with the blunt-instrument technique of the so-called Gothic horror tale".
 Campbell insisted on the same rational approach to fantasy that he required of his science fiction writers, and in the words of Clareson, this led to the destruction of "not only the prevalent narrative tone but also most of the trappings that had dominated fantasy from The Castle of Otranto and The Monk through the nineteenth century to Weird Tales".
 Unknown quickly separated itself from Weird Tales, whose fantasies still primarily aimed to produce fear or shock.
 The closest predecessor to Unknown was Thorne Smith, whose prohibition-era "Topper" stories also mixed fantasy with humor.
 Before Unknown, fantasy had received little serious attention, though on occasion writers such as James Branch Cabell had achieved respectability.
In Ashley's opinion, Unknown created the modern genre of fantasy, though commercial success for the genre had to wait until the 1970s.

Clareson also suggests that Unknown influenced the science fiction that appeared in Astounding after Unknown folded.
 According to this view, stories such as Clifford Simak's City series would not have appeared without the destruction of genre boundaries that Campbell oversaw.
Clareson further proposes that Galaxy Science Fiction and The Magazine of Fantasy & Science Fiction, two of the most important and successful science fiction and fantasy magazines, were direct descendants of Unknown.

Unknown is widely regarded as the finest fantasy magazine ever published: Ashley says, for example, that "Unknown published without doubt the greatest collection of fantasy stories produced in one magazine."
 Despite its lack of commercial success, Unknown is the most lamented of all science fiction and fantasy magazines; Lester del Rey describes it as having gained "a devotion from its readers that no other magazine can match".
 Edwards comments that Unknown "appeared during Campbell's peak years as an editor; its reputation may stand as high as it does partly because it died while still at its best".
Unknown was, along with Weird Tales, an important early influence on the fantasy genre.   In the foreword to From Unknown Worlds, in 1948, Campbell commented that fantasy before Unknown had been too much infused with "gloom and terror"; his approach in Unknown had been to assume that the "creatures of mythology and folklore" could be characters in an amusing tale as easily as they could be made part of a horror story. Horror stories, he said, had a place, but "horror injected with a sharp and poisoned needle is just as effective as when applied with the blunt-instrument technique of the so-called Gothic horror tale".  Campbell insisted on the same rational approach to fantasy that he required of his science fiction writers, and in the words of Clareson, this led to the destruction of "not only the prevalent narrative tone but also most of the trappings that had dominated fantasy from The Castle of Otranto and The Monk through the nineteenth century to Weird Tales".  Unknown quickly separated itself from Weird Tales, whose fantasies still primarily aimed to produce fear or shock.  The closest predecessor to Unknown was Thorne Smith, whose prohibition-era "Topper" stories also mixed fantasy with humor.  Before Unknown, fantasy had received little serious attention, though on occasion writers such as James Branch Cabell had achieved respectability. In Ashley's opinion, Unknown created the modern genre of fantasy, though commercial success for the genre had to wait until the 1970s.
Clareson also suggests that Unknown influenced the science fiction that appeared in Astounding after Unknown folded.  According to this view, stories such as Clifford Simak's City series would not have appeared without the destruction of genre boundaries that Campbell oversaw. Clareson further proposes that Galaxy Science Fiction and The Magazine of Fantasy & Science Fiction, two of the most important and successful science fiction and fantasy magazines, were direct descendants of Unknown.
Unknown is widely regarded as the finest fantasy magazine ever published: Ashley says, for example, that "Unknown published without doubt the greatest collection of fantasy stories produced in one magazine."  Despite its lack of commercial success, Unknown is the most lamented of all science fiction and fantasy magazines; Lester del Rey describes it as having gained "a devotion from its readers that no other magazine can match".  Edwards comments that Unknown "appeared during Campbell's peak years as an editor; its reputation may stand as high as it does partly because it died while still at its best".
Unknown (magazine)