From the December issue: Two record-breaking residential sales took the real estate industry by surprise last month. In early November, a mystery buyer signed a contract to pay a whopping $40 million for William Zeckendorf’s 41st-floor apartment at luxurious 15 Central Park West, the New York Post reported. At more than $10,000 per square foot, the sale will set a new Manhattan record when it closes. Then, entrepreneur Mark Shuttleworth reportedly closed on a $31.5 million penthouse at Superior Ink, setting another record — this one for the priciest apartment sale below 14th Street. [more]