I can't think of one set on autumn right now.But discworld has wizards,witches,werewolves,vampires,zombies,ect-all very halloween-y.And if you have a favorite character or place,you could do something fall-ish with them,even if it's not in a book. I keep thinking surely leonard of quirm,or bloody stupid johnson has to have invented a leaf raking device. Something cozy a constable might wear on patrol on these fall nights? Dragons make good fire starters.We can get very creative in our descriptions to make them fit!
If you are keeping your partner's favorite characters/places/personal preferences in mind, I don't think every single item has to be fall related.What do the rest of you think?