I feel like there must be a lot of autumnal fiction out there! NOw that I'm trying to think, any are of course eluding me - save obviously for all the many Halloween things, plus there are a few Bonfire Night ones as well. (THere's a Poirot short story where someone uses that to cover up gunfire.) Probably a few harvest-themed things as well, probably.

But one I can think of is Lord of the Rings - they pass through several seasons, but the mood is certainly autumnal for Middle Earth, with this age on the verge of passing away.