A lot of Halloween books are funnier than they are frightening, and that is the right level for a preschooler. They want a witch, a skeleton, or a monster they can boss around. They do not need a story that follows them down the hall.
Read these with the lights on and a silly voice. Room on the Broom and Big Pumpkin are crowd books. Children like to chant. Go Away, Big Green Monster! lets them tell the monster to leave, which matters if Halloween has started to feel like too much.
Creepy Carrots! looks spooky and then turns into a joke about a rabbit who ate too many vegetables. If a child is easily spooked, start with that one or with Skeleton Hiccups, and skip anything with a dark cover until next year.
One Halloween book at bedtime is plenty. Save the second reading for the afternoon.
Put the book away when it is done. A second spooky cover on the nightstand undoes the joke. Tomorrow they can pick the witch again if they still want her.