Don't be fooled. The description of the book makes it sound like it takes place during October, but it actually starts in June and the happens expand throughout the summer into October. I was a little disappointed in that.
Diana the witch comes to town and opens up a shop and no one seems to have a problem with her except over religious guy Ike who blames her for everything bad that is happening in Tinker's Cove. First the lack of water, then some fires that happen, then floods that come, the death of his wife, the illness of his daughter, etc. The book is pretty much just him blaming Diana for everything and Lucy trying to keep her kids from doing witchcraft. Yes, there is a mystery. A guy who turns out to be a witch is found burned to death in the woods behind Lucy's house, so she tries to find out who did it.
It was entertaining and a little creepy.