If you need an intriguing read for October, you might consider...
...The Case Against Satan, a brief 1962 novel by Ray Russell of Sardonicus fame. Somehow I had never heard of this one, now out in a respectable new edition by Penguin Classics if you please, but it's a gripping fast read, and it seems inarguably influential.
Set in a Roman Catholic rectory in a working-class Chicago neighborhood, Russell's book dramatizes an exorcism. At the time, apparently, this rite was so rarely performed and archaic that it was a novelty to readers it would not be a decade later, after the release of William Peter Blatty's 1971 novel The Exorcist and its 1973 movie adaptation popularized the concept.
In Russell's yarn, the possession victim is a pretty teenage girl. The exorcism is performed by a younger priest with a drinking problem and an interest in psychology and other "modern" ideas; he's supervised by his Bishop, an older, more traditional sort. The victim is bound to a bed, and at one point she has an upset tummy to a projectile degree.
In short, the book has broad resemblances to The Exorcist that seem unmistakable. Unlike Blatty, however, Russell leaves matters ambiguous; the story could, however unconvincingly, be interpreted in non-supernatural terms.
The author's narrative tone toward then-contemporary religious attitudes is snarky and contemptuous, referring, at the novel's opening, to the modern idea of God as "...a nodding Santa Claus with twinkling eyes and a spun glass beard..." and to modern religion as "...an unnatural thing of all light and no shadow, a pious bonbon so nice, so sweet, so soporifically bland that a Karl Marx can call it the opium of the people not without justice..." Russell, who died in 1999, lived long enough to see conservative religious attitudes in our culture swing the other direction; I don't know if he was comforted by this change or not.
I, for one, am fervently hoping for the Nodding Santa Claus. That said, if you're looking for a diabolical tale to pass an autumnal evening, rather than revisiting Rosemary's Baby or The Exorcist this year I'd suggest you pick the devil you don't know.
