More and more ghosts are being drawn to Oak Bluffs’ attractive summer housing. “Some spirits have a sliver of their psyche attached to some place where they were happy,” explains Holly Nadler, Haunted Island author, bookstore owner and part-time ghost-hunter. As these properties change owners more frequently, some are becoming crowded. “This place is gooey with ghosts,” said Ms. Nadler, conducting a tour of the Camp Ground last weekend.