This new listing at 321 Clinton Avenue is a charmer. The duplex co-op occupies part of the top two floors of a Clinton Hill mansion between Dekalb and Lafayette. The living room, with its double exposure, original details and attractive built-ins, looks great. The bedrooms on the top floor are defined by their dormer ceilings, which typically are not great for maximizing usable square feet but in this case seem to work just fine. The interior decoration is staged to sell as well. Asking price: $875,000.