I love the eerie feel of fog blanketing the parks and shadowing the streets. Such a minor setting element can change the feel of a town, a house or a create a whole character itself. One example of a great spectral setting is from my current book, The Darkest Part of the Forest by Holly Black. The forest in Fairfold comes alive with monsters, animals, and deadly fairies. It is the perfect read for a foggy morning, snuggled in with a warm drink.