Hallowe'en Party By Agatha Christie
You, my friend, seem like you would love the kind of story that treads just close enough to the dark that it doesn't become a full on horror, but also challenges you. Miss Agatha Christie is one of the most iconic mystery writers ever, and Hallowe'en Party is the kind of story that gives you just enough to solve the mystery alongside our hero, Hercule Poirot, wihtout holding your hand. If you'd like a story you can curl up with a mug of tea, a blanket, and every single light in the house on (its still a creepier story than usual), then this one would be for you.
Word to the wise though, head to your local library to give the book a read instead of buying it, that way you know if you'll enjoy it enough for a reread!
Happy reading!