Arthur Machen (1863–1947)
Probably the shortest title in the MR library. This is a short story about a window to another world opening in the dull London suburb of Stoke Newington.
The Machen Society webpage comments:
“The enigmatically titled "N", which Machen wrote when he was over seventy, is a kind of psychedelic fable which concerns the discovery of an alternate reality existing in the context of a humble, grey north London suburb. Machen's greatest power is thus, to bring together banal familiarity and impossible strangeness, to the great enhancement of both.”