I'm torn between these two books, still deciding. Both of them happen on/around halloween.
Something Wicked this Way Comes by Ray Bradbury
It's the week before Hallowe'en, and Cooger and Dark's Pandemonium, Shadow Show has come to Green Town, Illinois. The siren song of the calliope entices all with promises of youth regained and dreams fulfilled, but everyone touched will be destroyed, for Mr Dark collects souls. And as two boys trembling on the brink of manhood set out to explore the mysteries of the dark carnival's smoke, mazes and mirrors, they will also discover the true price of innermost wishes.
or
A Night in the Lonesome October by Roger Zelazny
Snuf, a guard dog who performs thaumaturgical calculations, accompanies his master, Jack, on collecting expeditions into the Whitechapel slums of nineteenth-century London.
Zelazny manages to cleverly combine Jack (the Ripper), Sherlock Holmes, Dr. Frankenstein, and Dracula together with witches, werewolves, druids and many others in this amusing tale of an approaching confrontation that, on the Halloween of a full-moon, will change the cosmic balance of power between good and evil. Told through the eyes of Snuf, Jack's guard dog, who performs magical calculations in addition to accompanying his master on collecting expeditions into 19th century London. Twists and turns of magical espionage and adventure unfold as this unforgettable tale plays out over the course of 31 lonesome nights in October.