Cosmic horror done (mostly) right.
This is an interesting little tale that draws heavily from the likes of Blackwood and Lovecraft for inspiration, without ever resorting to using those well-worn "Lovecraft-isms" that too many weird fiction authors seem to think are mandatory.
Spider from the Well is competently written and strikes just enough discordant notes to pull off its fairly ambitious premise given its short length. This is helped considerably by some pretty creepy imagery.
Better than most of the stories you'd find in an Ellen Datlow anthology.